Side channel pump is a kind of super-low specific speed radial vane pump which has small volume with low flow rate but high head. The fluid in the side channel pump travels in a spiral flow path and inherently leading to complex three-dimensional turbulent flows. These turbulent flows are accompanied with large numbers of axial and radial vortices during the operation of the pump. The vortices developed have direct influence of the performance, therefore it is very important to study and reveal the evolution of the vortices. In order to study the internal vortex characteristics of a side channel pump, unsteady numerical simulations were conducted on a traditional side channel pump impeller with convex blade through commercial software CFX 17.0. The accuracy and reliability of the numerical simulations were verified by experimental measurements. The Q-criterion method coupled with vorticity fluctuation was used to visualize and analyze the internal vortex structure. The results showed that the convex blade can increase the high efficient area of the side channel pump and broaden the application range of the side channel pump. However, compared with the general side channel pump, the head of the side channel pump with convex blade was slightly down. Compared with the inlet region and the side channel, the vortices developed within the pump with the convex blade mainly existed in the impeller passage. However, the vortices in the inner radius of impeller were greater than that of the outer radius, and the number of vortices near the inlet of the impeller was the largest and the most complicated. With the increase of flow rate, the vortices in the impeller become smaller and the number was significantly decreased except the inlet region of the impeller. The research results on the internal vortex characteristics can be used as a theoretical basis for the optimal design of efficient side channel pumps.