The topology structure of Transferring Southern Water to the North (TSWN) was designed on the basis of WholesaleRetail model of TSWN, and the function of contract to the project operation and benefits balance was described. According to the adoption and the operation principal, the Minimum commitment and Flexibility contract was chosen, each model was built up and the optimal order strategy of buyer was given. The allocation of the increased revenue because of flexibility and the combination of the longterm and the short-term contracts such as option contract would be researched further.