With the progress of coal-to-electricity project, power supply reliability evaluation of coal-to-electricity station has become an important topic. The power supply reliability evaluation model is established considering that the coal-to-electricity station is connected to the edge power supply during the power shortage period. The evaluation index model of power supply reliability considering the edge power supply is established by using the average power supply availability index. The evaluation process of power supply reliability in the coal-to-electricity station is constructed, and the probability distribution model of the grid-connected time of the edge power supply is established. On the basis of Monte Carlo simulation method, the assessment steps of power supply reliability are given based on the probability evaluation method for the operation state of the coal-to-electricity station. Finally, power supply reliability evaluation is carried out for a coal-to-electricity distribution station with edge power supply access. The effectiveness and rationality of the proposed method are verified by two evaluation scenarios for power supply reliability index evaluation and comparison.