When playing double bass seem like my left foot is slower than right so can't play complex pattern smoothly and fast. At first I thought is the drum pedal problem but when try with my right foot it is OK.

Practice with your left more often or start exercises with ur left.

There's no magical pill to make your less dominant limb as skillful as your dominant limb.

Ok Thnx. Cos when playing straight 16th double I kinda have no problem. But when playing patterns then I notice my left not that responsive. What pattern exercise is best to improve?

Any exercise , just switch to your left foot as the lead foot.
Incidentally, unresponsive left foot might be due to independence issue.

Like u learn anything new, keep practicing and go slow and accurately

Listen lots of complex music.. until you are natural with it. Limb independency is the key here

I think maybe need to develop left foot muscle. Probably go running or gym also can help