In order to optimize the double-channel pump impeller, inner flow field of the original pump was simulated and diagnosed by introducing boundary vorticity dynamics theory. Several positive and negative BVF peak areas were observed at different locations of the original impeller, which usually relates to large pressure gratitude and flow separation. By analyzing the distribution of BVF, friction and vorticity lines on the impeller surface, the locations of the bad flow inside the impeller and their dynamic roots were found. According to diagnosis of the flow, the structural parameters affecting inner flow state of the double-channel pump impeller were adjusted to obtain the optimized double-channel pump impeller. Combined with CFD and boundary vorticity dynamics flow diagnosis method, the double-channel pump impellers, before and after optimization, were compared and analyzed. The results showed that the distribution of BVF, friction and vorticity lines on the surface of optimized impellers had been significantly improved. The peak and mean values of BVF were both decreased apparently and the uniform index was much closer to 1. The flow separation was suppressed and force distribution was improved, therefore, the head and efficiency of the pump were improved obviously. The research work proved the feasibility of applying inner flow diagnosis and optimization method based on boundary vorticity dynamics theory in the channel impeller machinery, and it also provided reference for the study of optimization design of other turbomachinery.