With the increasing penetration rate of new energy in power grid, the uncertainty of new energy has a certain impact on power grid dispatching operation. Therefore, some new requirements are put forward for scheduling operation control technology. In order to directly express the real-time accommodation capacity of new energy in the power grid, and guide the maximized accommodation of new energy and the stable operation of the power grid, the main factors affecting the accommodation of new energy are analyzed in this paper firstly. On this basis, an optimization model of new energy real-time accommodation capacity considering the security constraints of network and sources is established. At the same time, an assessment method of new energy real-time accommodation capacity considering the uncertainty of new energy is proposed as well. The results of example show that the proposed method can reduce the influence of new energy uncertainty effectively and evaluate the maximum real-time accommodation capacity of new energy reasonably on the premise of ensuring the safe operation of power grid.