If I remove Debit card from Google Play store from which I bought some application how will it affect on the application that I bought from it?
It should have no effect. You've already paid, right? The money has already changed hands and the app payment is tied to your account, not the payment method.
L.L. Bean doesn't come and take back the socks you ordered if you cancel a credit card after the order was completed. Why would this be any different?
You'll only have an issue if you close down your Google account.