Microgrids are a new generation of power systems in small scale, which can fulfils the power requirements of their customers independently from the main power system. One of the characteristics of these systems is their ability to integrate distributed generation units with renewable energy sources, which are inherently probabilistic and intermittent. This, highlights the necessity of studying the reliability of the microgrid to make sure that enough reliability is maintained, and if necessary, to take measures to improve the reliability. In this paper, using the probabilistic methods, it is tried to optimize the combination of distributed generation units and electric vehicles with the goal of improving the reliability of the microgrid. Optimization of a combination of generating units along with electric vehicles to improve the reliability of microgrid, presenting a new method in charge and discharge plans for electric vehicles, and probabilistic modeling of the power injected to the microgrid are amongst the contributions of the present paper.