diff --git a/routers/repo/compare.go b/routers/repo/compare.go
index f8534f68b77..b9e14abfb87 100644
--- a/routers/repo/compare.go
+++ b/routers/repo/compare.go
@@ -339,12 +339,40 @@ func PrepareCompareDiff(
 	return false
 }
 
+// parseBaseRepoInfo parse base repository if current repo is forked.
+// The "base" here means the repository where current repo forks from,
+// not the repository fetch from current URL.
+func parseBaseRepoInfo(ctx *context.Context, repo *models.Repository) error {
+	if !repo.IsFork {
+		return nil
+	}
+	if err := repo.GetBaseRepo(); err != nil {
+		return err
+	}
+	if err := repo.BaseRepo.GetOwnerName(); err != nil {
+		return err
+	}
+	baseGitRepo, err := git.OpenRepository(models.RepoPath(repo.BaseRepo.OwnerName, repo.BaseRepo.Name))
+	if err != nil {
+		return err
+	}
+	ctx.Data["BaseRepoBranches"], err = baseGitRepo.GetBranches()
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
 // CompareDiff show different from one commit to another commit
 func CompareDiff(ctx *context.Context) {
 	headUser, headRepo, headGitRepo, compareInfo, baseBranch, headBranch := ParseCompareInfo(ctx)
 	if ctx.Written() {
 		return
 	}
+	if err := parseBaseRepoInfo(ctx, headRepo); err != nil {
+		ctx.ServerError("parseBaseRepoInfo", err)
+		return
+	}
 
 	nothingToCompare := PrepareCompareDiff(ctx, headUser, headRepo, headGitRepo, compareInfo, baseBranch, headBranch)
 	if ctx.Written() {
diff --git a/templates/repo/diff/compare.tmpl b/templates/repo/diff/compare.tmpl
index 1c8942d42fe..50a51c44acc 100644
--- a/templates/repo/diff/compare.tmpl
+++ b/templates/repo/diff/compare.tmpl
@@ -28,6 +28,11 @@
 						{{range .Branches}}
 							<div class="item {{if eq $.BaseBranch .}}selected{{end}}" data-url="{{$.RepoLink}}/compare/{{EscapePound .}}...{{if not $.PullRequestCtx.SameRepo}}{{$.HeadUser.Name}}:{{end}}{{EscapePound $.HeadBranch}}">{{$.BaseName}}:{{.}}</div>
 						{{end}}
+						{{if .Repository.IsFork}}
+							{{range .BaseRepoBranches}}
+							<div class="item" data-url="{{$.PullRequestCtx.BaseRepo.Link}}/compare/{{EscapePound .}}...{{$.HeadUser.Name}}:{{EscapePound $.HeadBranch}}">{{$.PullRequestCtx.BaseRepo.OwnerName}}:{{.}}</div>
+							{{end}}
+						{{end}}
 					</div>
 				</div>
 			</div>
@@ -54,7 +59,7 @@
 
 	{{if .IsNothingToCompare}}
     	<div class="ui segment">{{.i18n.Tr "repo.pulls.nothing_to_compare"}}</div>
-    {{else if .PageIsComparePull}}
+	{{else if .PageIsComparePull}}
 		{{if .HasPullRequest}}
         	<div class="ui segment">
         		{{.i18n.Tr "repo.pulls.has_pull_request" $.RepoLink $.RepoRelPath .PullRequest.Index | Safe}}
diff --git a/templates/repo/issue/list.tmpl b/templates/repo/issue/list.tmpl
index 9b354a6800b..d68e6dac26b 100644
--- a/templates/repo/issue/list.tmpl
+++ b/templates/repo/issue/list.tmpl
@@ -14,7 +14,7 @@
 					{{if .PageIsIssueList}}
 						<a class="ui green button" href="{{.RepoLink}}/issues/new">{{.i18n.Tr "repo.issues.new"}}</a>
 					{{else}}
-						<a class="ui green button {{if not .PullRequestCtx.Allowed}}disabled{{end}}" href="{{if .PullRequestCtx.Allowed}}{{.PullRequestCtx.BaseRepo.Link}}/compare/{{.PullRequestCtx.BaseRepo.DefaultBranch | EscapePound}}...{{if ne .Repository.Owner.Name .PullRequestCtx.BaseRepo.Owner.Name}}{{.Repository.Owner.Name}}:{{end}}{{.Repository.DefaultBranch | EscapePound}}{{end}}">{{.i18n.Tr "repo.pulls.new"}}</a>
+						<a class="ui green button {{if not .PullRequestCtx.Allowed}}disabled{{end}}" href="{{if .PullRequestCtx.Allowed}}{{.Repository.Link}}/compare/{{.Repository.DefaultBranch | EscapePound}}...{{if ne .Repository.Owner.Name .PullRequestCtx.BaseRepo.Owner.Name}}{{.Repository.Owner.Name}}:{{end}}{{.Repository.DefaultBranch | EscapePound}}{{end}}">{{.i18n.Tr "repo.pulls.new"}}</a>
 					{{end}}
 				</div>
 			{{else}}