diff --git a/backend/src/app.ts b/backend/src/app.ts
index 648d71e..d5efbdc 100644
--- a/backend/src/app.ts
+++ b/backend/src/app.ts
@@ -5,6 +5,7 @@ import Debug from 'debug'
 import koaBody from 'koa-body'
 import func from './func'
 import { ErrorDescEnum, HttpError } from './types/HttpError'
+import { PrismaClient } from '@prisma/client'
 
 dotenv.config()
 console.log = Debug('invoiceIssuer:app.ts')
@@ -12,10 +13,13 @@ console.log = Debug('invoiceIssuer:app.ts')
 const app = new Koa()
 app.use(koaBody())
 
-// 错误处理中间件
+// 语境中间件
 app.use(async (ctx, next) => {
 	try {
+		const prismaClient = new PrismaClient()
+		ctx.prisma = prismaClient
 		await next()
+		prismaClient.$disconnect()
 	} catch (e) {
 		if (e instanceof HttpError) {
 			ctx.status = e.status
@@ -65,7 +69,7 @@ app.use(route.post('/payer', async (ctx) => {
 	if (abn && !abnRegex.test(abn)) throw new HttpError(ErrorDescEnum.invalid_field_format, 400, ['abn'])
 
 	// 创建新的付款人
-	await func.createPayer(name, address, email, abn)
+	await func.createPayer(ctx.prisma, name, address, email, abn)
 	ctx.status = 204
 }))
 
diff --git a/backend/src/func/createPayer.ts b/backend/src/func/createPayer.ts
index 796c1cc..dedf362 100644
--- a/backend/src/func/createPayer.ts
+++ b/backend/src/func/createPayer.ts
@@ -1,5 +1,6 @@
 import Debug from 'debug'
-import { PrismaClient } from '@prisma/client'
+import { ErrorDescEnum, HttpError } from '../types/HttpError'
+import { PrismaClient, Prisma } from '@prisma/client'
 
 console.log = Debug('invoiceIssuer:func/createPayer.ts')
 
@@ -11,24 +12,23 @@ console.log = Debug('invoiceIssuer:func/createPayer.ts')
  * @param {string} email - 付款人的电子邮件地址
  * @param {string} abn - 付款人的澳大利亚商业号码
  */
-export default async (name: string, address: string[], email: string, abn?: string) => {
-	const prisma = new PrismaClient()
+export default async (prisma: PrismaClient<Prisma.PrismaClientOptions, never>, name: string, address: string[], email: string, abn?: string) => {
+	// 验证 ABN 是否已存在
+	const existingPayer = await prisma.payer.findFirst({
+		where: {
+			payer_abn: abn
+		}
+	})
+	if (existingPayer) throw new HttpError(ErrorDescEnum.item_exists, 400, ['abn'])
 
-	try {
-		// 创建新的付款人
-		const payer = await prisma.payer.create({
-			data: {
-				payer_name: name,
-				payer_address: address.join('\n'),
-				payer_email: email,
-				payer_abn: abn
-			}
-		})
-		return payer
-	} catch (e) {
-		console.log(e)
-		throw new Error('unknown_issues')
-	} finally {
-		await prisma.$disconnect()
-	}
+	// 创建新的付款人
+	const payer = await prisma.payer.create({
+		data: {
+			payer_name: name,
+			payer_address: address.join('\n'),
+			payer_email: email,
+			payer_abn: abn
+		}
+	})
+	return payer
 }
\ No newline at end of file
diff --git a/backend/src/types/HttpError.ts b/backend/src/types/HttpError.ts
index 88347f0..c709b30 100644
--- a/backend/src/types/HttpError.ts
+++ b/backend/src/types/HttpError.ts
@@ -34,14 +34,21 @@ enum ErrorDescEnum {
 	 * 必填字段缺失。通常与 HTTP 状态码 400 Bad Request 一起使用。
 	 */
 	required_fields_missing = 'required_fields_missing',
+
 	/**
 	 * 字段格式不正确。通常与 HTTP 状态码 400 Bad Request 一起使用。
 	 */
 	invalid_field_format = 'invalid_field_format',
+
 	/**
 	 * 未知错误。通常与 HTTP 状态码 500 Internal Server Error 一起使用。
 	 */
-	unknown_issues = 'unknown_issues'
+	unknown_issues = 'unknown_issues',
+
+	/**
+	 * 项目已存在。通常与 HTTP 状态码 400 Bad Request 一起使用。
+	 */
+	item_exists = 'item_exists'
 }
 
 export { HttpError, ErrorDescEnum }
\ No newline at end of file