To evaluate the reliability of active distribution networks, there is a need to model distributed generation sources, mainly renewable ones. The traditional (common) reliability models are not able to take into account the intermittent and random nature of these energy sources, so the need for a new reliability model is necessary to model the production sources of this type of distribution network. In analytical methods, an analytical model of the network is prepared and the problem is solved mathematically; but with the complexity of the network, solving problems becomes very difficult and practically impossible. Therefore, in terms of the complexity of the structure and the variety of operating modes of active distribution networks, a simulation [Monte Carlo] method has been proposed to evaluate their reliability. In this method, all failure modes of network components are randomly classified and specified. On the other hand, by using the proposed model of reliability of DGs, the nature of randomness of these sources has been accurately considered in the simulation process. The simulation results of a sample active distribution network indicate that, with the introduction of microgrids, the reliability indicators of the network and its loads have improved, but the microgrid has had the greatest impact on the load indicators within the microgrid itself.