MoSi2 coatings were prepared on 45CrNi substrate by supersonic plasma spraying. The tribocorrosion resistance of MoSi2 coating and post-treated MoSi2 coating (P-MoSi2) in the seawater environment was analyzed. After post-treatment, some new phases such as MoO3, SiO2 and Mo9O26 are generated in the P-MoSi2 coating. The electrochemical test results indicated that the P-MoSi2 coating has lower current density, larger βc and Rp values than MoSi2 coating in both static corrosion and tribocorrosion tests. The wear test results indicate that the post-treatment reduced the wear rates and the friction coefficients of the coating. The wear mechanisms of both coatings were described to explain the differences. Moreover, the mechanism of the improved tribocorrosion resistance of the coating after post-treatment was explained.