Atomic Force Microscopy(AFM) plays a very important role in researching crystal growth mechanism, especially protein crystals. The principle of AFM for protein crystal examination is briefly described as well as the importance of research on protein crystal growth, known growth mechanisms including 2-D steps nucleation, spiral dislocation, normal growth, 3-D nucleation and anisotropic development, and latest progress about eucommia antifungal protein(EAFP) and Trichosanthin(TCS) protein crystal growth mechanism, respectively. Finally, protein growth under microgravity environment is also expounded here and their development tendency and practical prospect.