Hello everyone, I think I just changed the IP of VPS, how should I operate?

You update whatever is pointing to the old IP (e.g. DNS) to the new IP.

To piggyback off of what @Woet mentioned (which is correct), I wanted to direct you to another post here on our Community Questions site that I put together awhile back that gives you the basics of DNS configuration using our system. I hope it's helpful:

How do I configure DNS for my Linode?

I also wanted to give you some extra tips. You mentioned that you think you've changed your Linode's IP address. You can check which address is assigned in Cloud Manager from the Networking tab. Then, you can run the below commands from within your Linode to confirm that the address matches.

Debian/Ubuntu
To view your network interface file:
cat /etc/network/interfaces

The next two commands will confirm, or deny, that your Linode's routing tables have the correct IP address.
ip a
ip r

CentOS
To view your network interface file:
cat /etc/sysconfig/network-scripts/ifcfg-eth0

The next two commands are the same for CentOS:
ip a
ip r