The invention relates to a demand side interconnection reliability evaluation method and system, comprising the steps of calculating system power flow based on a system state obtained by sampling; judging whether the system power flow obtained by calculation satisfies the constraint conditions; if yes, returning to the last step to continue to calculate the system power flow until the sampling times reach the preset sampling times; if not, performing load shedding processing on the demand side, and taking minimum load shedding amount as the objective to calculate the system power flow. Based on the calculation result of the system power flow, the power system reliability evaluation index under the demand side interconnection is calculated, and the power system reliability under the demandside interconnection is evaluated based on the reliability evaluation index. Through the abovementioned scheme, the accurate reliability evaluation of demand side interconnection effect can be achieved.