// 细节: 本界面上设置, 下个界面上显示  

// 方式一  

self.navigationItem.backBarButtonItem = [[UIBarButtonItem alloc] initWithTitle:@"返回" style:UIBarButtonItemStylePlain target:nil action:nil];  

// 方式二  

UIBarButtonItem * backButtonItem = [[UIBarButtonItem alloc] init];  

backButtonItem.title = @"返回";  

self.navigationItem.backBarButtonItem = backButtonItem;  

修改返回键

摘自：https://blog.csdn.net/u011096206/article/details/50606778