Different working scheme has different design flow in delivery and distribution pipe for irrigation that will influence the project investment. The optimal design of irrigation pipe networks based on rotational irrigation method that applied genetic algorithms (GA) with integer code was studied, the number of rotation was taken into account to optimize for the first time. VB and Matlab mixed programming in the computer realization process was used by this method. The optimal results showed that the proposed method is evidently good and could be used in practice.