Xiaomi Phones are not officially accepted in JIO Network you can still try your luck by using the steps given below to grab Jio SIM.
How to get Reliance Jio Sim for Xiaomi Devices (Redmi Note 3, Redmi 3s/3s Prime,Mi5, Mi Max)
1: Uninstall My Jio app if you have previously installed in your Xiaomi Device.
2: Download My Jio App (V3.2.05)
(Link : http://mostusefuldrills.com/downloading-myjio-apk)
3: Disconnect your WiFi and Mobile data.
4: Install My Jio app (V3.2.05).
5: Open My Jio app, and click on “Open” next to My Jio. It’d be throwing “No internet connection” error on top, but don’t care about it.
Now opens the Login screen, and there you’d see the Get Jio Sim button.
6: Click on it, and it’d throw an error about internet not being available. At this point, switch back your WiFi and tap back to go to the login screen again.
Now click on Get Jio Sim button and boom! It will show the preview offer screen and lets you generate the activation/offer code.