代码：

using UnityEditor;
using UnityEngine;
using System.Collections.Generic;
using System.IO;

public class SearchRefrenceEditorWindow : EditorWindow
{
    /// <summary>
    /// 查找引用
    /// </summary>
    [MenuItem("Assets/SearchRefrence")]
    static void SearchRefrence()
    {
        SearchRefrenceEditorWindow window =
            (SearchRefrenceEditorWindow) EditorWindow.GetWindow(typeof(SearchRefrenceEditorWindow), false, "Searching",
                true);
        window.Show();
    }

    private static Object searchObject;
    private List<Object> result = new List<Object>();

    private void OnGUI()
    {
        EditorGUILayout.BeginHorizontal();
        searchObject = EditorGUILayout.ObjectField(searchObject, typeof(Object), true, GUILayout.Width(200));
        if (GUILayout.Button("Search", GUILayout.Width(100)))
        {
            result.Clear();

            if (searchObject == null)
                return;

            string assetPath = AssetDatabase.GetAssetPath(searchObject);
            string assetGuid = AssetDatabase.AssetPathToGUID(assetPath);
            //只检查prefab
            string[] guids = AssetDatabase.FindAssets("t:Prefab", new[] {"Assets"});

            int length = guids.Length;
            for (int i = 0; i < length; i++)
            {
                string filePath = AssetDatabase.GUIDToAssetPath(guids[i]);
                EditorUtility.DisplayCancelableProgressBar("Checking", filePath, i / length * 1.0f);

                //检查是否包含guid
                string content = File.ReadAllText(filePath);
                if (content.Contains(assetGuid))
                {
                    Object fileObject = AssetDatabase.LoadAssetAtPath(filePath, typeof(Object));
                    result.Add(fileObject);
                }
            }

            EditorUtility.ClearProgressBar();
        }

        EditorGUILayout.EndHorizontal();

        //显示结果
        EditorGUILayout.BeginVertical();
        for (int i = 0; i < result.Count; i++)
        {
            EditorGUILayout.ObjectField(result[i], typeof(Object), true, GUILayout.Width(300));
        }

        EditorGUILayout.EndHorizontal();
    }
}

t:Prefab 为类型，不需要改为""即可

或：

using System.Collections.Generic;
using System.IO;
using UnityEngine;
using UnityEditor;

public class AssetBeDepend
{
    // 存储所有依赖关系
    private static Dictionary<string, List<string>> referenceCacheDic;

    // 在 Assets 文件件下鼠标右键弹板中添加按钮 AssetBeDepend
    [MenuItem("Assets/AssetBeDepend")]
    static void Select()
    {
        referenceCacheDic = new Dictionary<string, List<string>>();
        CollectDepend();

        // 获取所有选中 文件、文件夹的 GUID
        string[] guids = Selection.assetGUIDs;
        foreach (var guid in guids)
        {
            // 将 GUID 转换为 路径
            string assetPath = AssetDatabase.GUIDToAssetPath(guid);
            IsBeDepend(assetPath);
        }
    }

    // 收集项目中所有依赖关系
    static void CollectDepend()
    {
        int count = 0;
        // 获取 Assets 文件夹下所有资源
        string[] guids = AssetDatabase.FindAssets("");
        foreach (string guid in guids)
        {
            // 将 GUID 转换为路径
            string assetPath = AssetDatabase.GUIDToAssetPath(guid);
            // 获取文件所有直接依赖的资源
            string[] dependencies = AssetDatabase.GetDependencies(assetPath, false);

            foreach (var filePath in dependencies)
            {
                // dependency 被 assetPath 依赖了
                // 将所有依赖关系存储到字典中
                List<string> list = null;
                if (!referenceCacheDic.TryGetValue(filePath, out list))
                {
                    list = new List<string>();
                    referenceCacheDic[filePath] = list;
                }

                list.Add(assetPath);
            }

            count++;
            EditorUtility.DisplayProgressBar("Search Dependencies", "Dependencies",
                (float)(count * 1.0f / guids.Length));
        }

        EditorUtility.ClearProgressBar();
    }

    // 判断文件是否被依赖
    static bool IsBeDepend(string filePath)
    {
        List<string> list = null;
        if (!referenceCacheDic.TryGetValue(filePath, out list))
        {
            return false;
        }

        bool isMan = false;
        // 将依赖关系打印出来
        foreach (var file in list)
        {
            Debug.LogError(filePath + "   被:" + file + "    引用", AssetDatabase.LoadAssetAtPath<Object>(file));
        }

        return true;
    }
}