This paper studies genotypes entropy and gametes’ mutual information of a pair alleles population in mating of homologous phenotypes. In mating of homologous phenotypes, the genotypes entropy of a pair alleles population is monotonically decreasing by generation number from the beginning of equilibrium of random mating. The decrease of genotypes entropy becomes slower and slower, and finally tends to zero. With the decrease of genotype entropy, the genetic diversity degree of population also decreases. In mating of homologous phenotypes, the gametes’ mutual information of a pair alleles population is monotonically increasing by generation number from the beginning of equilibrium random mating. The increase of mutual information becomes slower and slower, finally tends to zero. The increase of gametes’ mutual information shows that passed information between gametes becomes more and more, and that the fact is better reflected by information coefficient of mating of homologous phenotypes. At last, the conclusions are tested by computer imitation.