To analyze the functional divergence between groups and predict the amino acid residues resulting in functional difference, program DIVERGE (Gu and Velden, 2002) was applied to calculate the coefficient of type I functional divergence θI as well as that of type II functional divergence θII. The likelihood test is approximated to a χ2 distribution with 1 degree of freedom. After duplication, a significant θI means site-specific changed selective constraints (Xun, 2003; Gu, 2006; Yang et al., 2009). After duplication, a significant θII, indicates amino acid physiochemical property's obvious shifts (Xun, 2003; Gu, 2006; Yang et al., 2009).