The invention discloses a credible capacity calculating method for distributed grid connection of multiple types of power supplies. The credible capacity calculating method comprises the following steps: 1, integrating the multiple types of power supplies by using a virtual power plant, making a daily generation plan of the multiple types of power supplies in each hour according to the contribution features of the multiple types of power supplies, network information and a power grid settlement way, and forming a daily scheduling model of the virtual power plant; 2, performing analog simulation on wind speed, incoming water information and random failures of circuits in the virtual power plant by using a sequential Monte Carlo sampling method, and combining the daily scheduling model to obtain an annual time sequence contribution curve of the virtual power plant; and 3, calculating the credible capacity of the virtual power plant by adopting an effective load method on the basis of an equivalent energy function method according to the annual time sequence contribution curve of the virtual power plant and an overall annual time sequence load curve of a power grid. Through adoption of the credible capacity calculating method, the problems of failure in effectively determining the credible capacity of the virtual power plant and the like due to the adoption of a conventional credible capacity calculating method based on an equivalent energy function are solved.