diff --git a/pkg/render/openresty/status_codes.go b/pkg/render/openresty/status_codes.go
new file mode 100644
index 00000000..65c4b006
--- /dev/null
+++ b/pkg/render/openresty/status_codes.go
@@ -0,0 +1,62 @@
+package openresty
+
+import (
+	"fmt"
+	"sort"
+	"strconv"
+	"strings"
+)
+
+const (
+	StatusCodeMin = 400
+	StatusCodeMax = 599
+)
+
+func ParseStatusCodeTag(tag string) (lo, hi int, err error) {
+	tag = strings.TrimSpace(tag)
+	if tag == "" {
+		return 0, 0, fmt.Errorf("状态码标签不能为空")
+	}
+	if i := strings.IndexByte(tag, '-'); i >= 0 {
+		lo, err = strconv.Atoi(tag[:i])
+		if err != nil {
+			return 0, 0, fmt.Errorf("无效状态码区间: %s", tag)
+		}
+		hi, err = strconv.Atoi(tag[i+1:])
+		if err != nil {
+			return 0, 0, fmt.Errorf("无效状态码区间: %s", tag)
+		}
+	} else {
+		lo, err = strconv.Atoi(tag)
+		if err != nil {
+			return 0, 0, fmt.Errorf("无效状态码: %s", tag)
+		}
+		hi = lo
+	}
+	if lo > hi {
+		return 0, 0, fmt.Errorf("状态码区间左右端点反序: %s", tag)
+	}
+	if lo < StatusCodeMin || hi > StatusCodeMax {
+		return 0, 0, fmt.Errorf("状态码须在 %d–%d: %s", StatusCodeMin, StatusCodeMax, tag)
+	}
+	return lo, hi, nil
+}
+
+func ExpandStatusCodeTags(tags []string) ([]int, error) {
+	set := map[int]struct{}{}
+	for _, tag := range tags {
+		lo, hi, err := ParseStatusCodeTag(tag)
+		if err != nil {
+			return nil, err
+		}
+		for c := lo; c <= hi; c++ {
+			set[c] = struct{}{}
+		}
+	}
+	out := make([]int, 0, len(set))
+	for c := range set {
+		out = append(out, c)
+	}
+	sort.Ints(out)
+	return out, nil
+}
diff --git a/pkg/render/openresty/status_codes_test.go b/pkg/render/openresty/status_codes_test.go
new file mode 100644
index 00000000..461672cd
--- /dev/null
+++ b/pkg/render/openresty/status_codes_test.go
@@ -0,0 +1,27 @@
+package openresty
+
+import "testing"
+
+func TestExpandStatusCodeTags(t *testing.T) {
+	t.Parallel()
+	codes, err := ExpandStatusCodeTags([]string{"500-502", "522", "501"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	// want sorted unique: 500,501,502,522
+	if len(codes) != 4 || codes[0] != 500 || codes[3] != 522 {
+		t.Fatalf("got %v", codes)
+	}
+	_, err = ExpandStatusCodeTags([]string{"399"})
+	if err == nil {
+		t.Fatal("expected error")
+	}
+	_, err = ExpandStatusCodeTags([]string{"503-500"})
+	if err == nil {
+		t.Fatal("expected reverse range error")
+	}
+	_, err = ExpandStatusCodeTags([]string{"5xx"})
+	if err == nil {
+		t.Fatal("expected syntax error")
+	}
+}