Abstract: In this study, colonization efficiency of the two mating-type Beauveria bassiana (MAT1-1-1, mating-type I; MAT1-2-1, mating-type II) in maize was assessed and the mating-type gene sequences of recovered B. bassiana strains were analyzed to reveal the host plants selection rules between the two mating-type strains and the environmental adaptability of different mating-type strains during colonization process. Four inoculation trials were applied as follows: BbOFDH1-5 (mating-type I) (treatment B5); BbDPSD2 (mating-type II) (treatment B2); mating-type I/mating-type II mixed equally (treatment B5+B2) and control (CK), spore concentration for treatment B5, B2 and B5+B2 was 10⁸ spores/mL and zero for control. Results showed that endophytes were detected in treatment B5, B2 and B5+B2 in corn leaves. Detection rates showed treatment B2 with mating-type II strain got a higher detecting rate of 33.00% than that of treatment B5 with mating-type I strain. In treatment B5+B2, the recovered endophytes had a higher rate with mating-type II strains than mating-type I strain with ratio 12:10. Among the mating-type I B. bassiana strains recovered from treatment B5 and B5+B2, MAT1-1-1 gene sequence analysis showed that multiple mutation loci in the non-coding region were observed while only three mutation loci in the coding region during the endophytic colonization process. However, no mutation was found about MAT1-2-1 gene from all the strains recovered from treatment B2 and B5+B2. In conclusion, mating-type II strain BbDPSD2 had a higher colonization efficiency than that of mating-type I strain BbOFDH1-5; corn plants prefered mating-type II strain BbDPSD2 to mating-type I strain BbOFDH1-5 as endophytic fungus; the mating-type gene MAT1-1-1 had a higher mutation rates than that of MAT1-2-1 significantly indicated that mating-type I strain had stronger environmental adaptability than that of mating-type II strain.