The invention discloses a new energy penetration rate assessment method based on probability power flow calculation, and belongs to the technical field of power system automation. The method combines the impact on a power grid from the variability and instability of wind/solar hybrid generation and the external load level and the change condition thereof. The method takes static stable constraint and reactive power control of a power system as conditions, obtains the change range of the voltage of an output common grid-connected point of a wind/solar hybrid generation station through probability power flow calculation, takes the specified range of the voltage of the grid-connected point as the index, and carries out the assessment of the maximum capability that the wind/solar hybrid generation station is connected to the power grid. The method can improve the safe and stable operation level of the wind/solar hybrid generation station, effectively guarantees the generation of the wind/solar hybrid generation station, and improves the energy-saving and emission reduction benefits.