An M-type section had been designed to reduce internal shock losses in the channel of votex pump. The reasonable M section was based on the theory of the same area, with the constant height, section of channel sharped like an M was more in line with law of fluid flow. The nearest distance of the wall of channel and the outlet of blades was 1mm. In order to research the inner flow in channel, computational fluid dynamics software CFX was adopted in the inner flow field analysis. Head, efficiency curve and velocity vector of rectangular and M-type channel were obtained from the simulation. The results show that the head and efficiency have improved; fluid flows more smoothly in the M-type channel; turbulence and small reverse spiral at the outlet of blades is less. However, the friction losses increase with the larger flow area.