I'm a Bangladeshi citizen&my wife US green card holder Chinese,to visit hongkong do we need visa?

Yes, you have to apply for a HK visa. For your wife, she can stay in HK within a week if you enters HK from the US. If she enters from mainland China, she has to apply for her Chinese laissez-passer to Hongkong. If she enters HK from mainland China but doesn't come back to China, she can stay there for a week.