Abstract: An in-depth study on the problem of optimum hydraulic design for a pump system with low head has been made in this paper.The efficiency of a pump system with low head is divided into two aspects: one is pump efficiency and the other is conduit efficiency.Some problems about the definition of pump segment in the pump system,efficiency modification for the pump segment and flow pattern of inlet conduit in the pump system are discussed.The influence of conduit hydraulic loss on the conduit efficiency and pump system efficiency is analyzed and the influence of both flow velocity and flow pattern on the conduit hydraulic loss is illustrated by calculation samples,from which the conclusions are drawn as follows: under the condition of low head,the key problem of how to increase the pump system efficiency is to reduce the conduit hydraulic loss as much as possible;The essential way to reduce the conduit hydraulic loss may be to lower the flow velocity and improve the flow pattern in the conduit.The approaches to reduce the conduit hydraulic loss mainly include: to choose the type of pump system and conduit with the optimal hydraulic performance,to suitably lower pump nD value,to choose better pump model,to suitably relax the restrictions for conduit control size,and to sufficiently optimize hydraulic design for conduit shape.