Taking the utilization degree of gravity head, the design's utilization rate of pressure drop created by hypsography was evaluated by using two different expressions namely utilization rate of pipe gravity head and utilization rate of path gravity head as network optimization objective functions. Line-up competition algorithm (LCA) with the two means competition that between families and inside a family and little controls parameter was introduced in optimal design. The result testified by the case study, and the comparison between the method based on minimization of cost and genetic algorithm showed that the new method could obtain the optimal result and is superior in search efficiency.