I have a mikrotik router (doesn't have a wireless interface) and a tenda ap and a openwrt installed router. I have a hotspot server in that mikrotik and My tenda access point connected to mikrotik though a lan cable (when someone tries to connect with tenda access point then mikrotik hotspot log in page occured. I want the same thing to happen with openwrt router) now I want to connect openwrt router to tenda access point wirelessly as a dump ap ( want to provide All the IPs by the main mikrotik router. So when someone will connect openwrt router they will be redirected to mikrotik hotspot log in page.)
sounds to me you want https://openwrt.org/docs/guide-user/network/wifi/relay_configuration, not a dumb ap.
Providing IPs from Main router but not redirecting to hotspot log in page
is this a client that haven't already been authenticated by the portal ?
Connect the Ethernet cable to a laptop instead of the AP and confirm it works properly as a captive portal. If it does not there is a problem in the Mikrotik configuration.
A dumb AP works as a wired to wireless converter without routing or interpreting any of the traffic, so wireless clients should also have captive portal the same as with the laptop test.
Portal opens in the openwrt router but the problem is when logging in the portal openwrt Mac address is used instead of my Device Mac address so when other devices connect the openwrt instead of opening portal they get direct internet connection.
It's not configured as a dumb AP then. In a dumb AP the wireless AP and the Ethernet connection upstream would be in the same kernel bridge, usually br-lan if you have only one AP running in the box.
What should I do now ? 
(re)configure your current "AP" based on https://openwrt.org/docs/guide-user/network/wifi/dumbap
although it's not running openwrt is it? so you might be screwed.