To study helium (He) supersonic molecular beam injection (SMBI) into H-mode tokamak plasma, a simplified multicomponent-plasma model under the assumption of quasi-neutral condition is developed and implemented in the frame of BOUT++. The simulation results show that He species propagate inwards after He SMBI, and are deposited at the bottom of the pedestal due to intensive ionization and weak spreading speed. It is found that almost all injected helium particles strip off all the bounded electrons. He species interact intensively with background plasma along the injection path during He SMBI, making deuterium ion density profile drop at the He-deposited location and resulting in a large electron temperature decreasing, but deuterium ion temperature decreasing a little at the top of the pedestal.