The most important factor that should be considered in managing a watershed is, taking into account objectives under policies. In operating from water resources systems, in general, and in reservoir, in particular, operating rules should be extracted as multi-objective. In this paper, multi-objective genetic programming (MOGP) is developed and used. Then, after verification, it is used to extract the reservoir multi-objective operating policy. In the present study, each operating policy is extracted with approach of minimization of the vulnerability approach (as the first objective) and maximization of the reliability (as a second objective). The verification results show that the performance of introduced tool is successful (with a coefficient of determination equal to 0.997) and it can be used for the multi-objective problems in the management of water resources systems, so that the range of vulnerability changes is between 16 to 41% and the range of reliability changes is between 46 to 78%.