Increasing demand of electrical energy has leaded to utilization of more and more Distributed generation (DG) sources in distribution systems. Since the locations and capacities of the DG sources connected to the distribution system profoundly impact on reducing system loss and improving system reliability, so placement and sizing indication of DGs is the most substantial process in distribution systems. By adding the reliability objective to this problem, it becomes more complicated than before and it needs to be solved with an accurate algorithm. To this reason, to solve the proposed problem a new approach based on the mixture of two algorithms named as Particle Swarm Optimization (PSO) and the Shuffle Frog Leaping algorithm (SFLA) is applied in this paper. A meticulous performance analysis is fulfilled on a 33-bus system in order to demonstrate the effectiveness of the presented methodology.