After I book a hotel with Ctrip, it sends a message to confirm. Do I need to reply to the message? Thanks!

If you chose SMS confirmation at that time, she only sent the message to verify your information. If your information is correct, there is no need to reply. If the information and check-in time are wrong, you need to make a phone call. Talk to her. I often travel on business so I often use Ctrip to book hotels, but I ask her to call to confirm every time, so that it is clearer.

I hope my personal experience will be helpful to you.