Non-Leptonic Two Body B Decays in QCD

We review the current status of theoretical study of non-leptonic two body B decays. There are two independent directions for this purpose. One is the so called QCD factorization approach (or BBNS approach), which is based on naive factorization approach. The other one is named perturbative QCD approach. We list the different ideas and applications of the two method, and make a comparison between the two.