how to open my ios Application by scanning QR Code from ios market app?

Before doing this you should Custom URL Scheme register for your app

Registering a Custom URL Scheme

After these steps you need to make QR code for your app and store in local DB of that app you're using. When scan QR code then get your app custom url and using this url you can open your app easily. Try this may be help full

after get Your custom url of your app try this for open application..

UIApplication *ourApplication = [UIApplication sharedApplication];
NSString *ourPath = @"your app Custom URL"; //For Example Like this @"com.myCompany.myapp"
NSURL *ourURL = [NSURL URLWithString:ourPath];
[ourApplication openURL:ourURL];