It's easy for your question. Look at your topology as below:
Main router(DHCP disable)——(WAN port)TL-WA5210G(AP Router mode, DHCP enable)(wireless LAN port)))))))))))((((((((((Clients

First of all, there is one and only one DHCP server needed in each LAN.
And in your topology, you get two LANs:
1. Main router and WAN port of TL-WA5210G in 192.168.1.x network segment;
2. TL-WA5210G's LAN port and the back-end clients in 192.168.2.x network segment(Since TL-WA5210G is in AP Router mode, it's a router as well. It makes up a LAN with the devices connected to it).
Therefore, you need to configure two DHCP server in your case while you only provide one(You have disabled the DHCP on main router).

Solutions is so easy:
1. Enable the DHCP in your main router(not recommended).
2. Configure the TL-WA5210G in AP mode as before with DHCP disable and enable DHCP on main router.

thanx alot for your reply
but actually I didn't disable the DHCP on the main router!
I told you that 5210 got ip address from the main router but when it gives ip addresses to users there is no internet access!!
I tried to connect Tp-link 843nd router instead of 5210 and it worked fine but when I reconnect 5210 again it gives ip addresses but without internet access

Sorry for my mistakes.
Would you please attach the screenshot of status tab of TL-WA5210G?
What IP can users got? Can the users PING router?

I attached the screeshot
users got ip like 192.168.2.xxx

They can't access root router because it is on different subnet
router ip 192.168.1.1

Login the web management page, navigate to Wireless > Distance Setting, Choose 'Indoor' in the drop-down list.

stupidbird wrote

Login the web management page, navigate to Wireless > Distance Setting, Choose 'Indoor' in the drop-down list.

I tried it but still there is no internet access at all

1. What's the DNS and Gateway in your PC?
2. Do the below PING test and give us the feedback: a. PC ping 192.168.2.252
b. PC ping 192.168.1.74
c. PC ping 192.168.1.1
d. PC ping 8.8.8.8
e. PC ping www.google.com
3. Check if the main router has block the TL-WA5210G(MAC filter of IP blacklist).