A mathematical model of the effect of velocity distribution asymmetry in heat exchanger channels on the heat transfer performance was formulated．The deviation of heat transfer duty in heat exchangers caused by the asymmetry was investigated when the fluid flowed inside the tubes or across the tube bundles．Research results indicate that the effect of velocity distribution asymmetry in exchanger channels on the heat transfer performance is not great．The deviation of heat transfer duty inside the tubes and across the tube bundles are both less than1％ when the velocity difference reaches100％ at uniform wall temperature and without heat transfer among channels．