Abstract: Inefficiency and counter-intuitive results are often generated by using optimization algorithm alone for deriving joint-operation rule curves of large-scale multi-reservoirs. This paper describes a simplification method for deriving the rule curves via a case study of the north-line inter-basin water transfer-supply project in Liaoning Province, China. The framework of this new method was derived by considering three aspects: the basic pattern of conventional hedging rule curves for major water users of aggregation reservoirs, the mean period distribution of water surplus and shortage, and the heuristic information including operation experiences and laws. Then, we developed an optimization-simulation model using this new method. The results show that the method brings about an easier searching of optimal solution in optimization algorithm and improves rationality and practicability of joint rule curves.