The invention discloses a transient stability 
risk assessment method considering the uncertainty of a 
new energy unit, which generates a predicted fault based on the current operation state of a powernetwork and performs 
transient stability assessment, and identifies a transient stability key transmission section corresponding to the fault. According to the short-term wind and 
light intensity forecasting results, the output interval probabilities of each 
new energy power 
plant are obtained, and the power intervals and their probabilities of the key transmission sections are calculated by probabilistic 
tidal current calculation. In order to increase the output of 
new energy units and evaluate the severity of the fault, the section power interval operating risk is accumulated as a fault 
risk index. If the 
risk index of the fault is greater than the threshold value, the measures to reduce the output of the conventional unit shall be taken first under the premise of giving priority to ensure the output of the new energy power 
plant, and if the requirements are not met, the 
risk index shall be ensured to be less than the threshold value by limiting the output of the new energy power 
plant. The method of the invention can comprehensively reflect the operating conditions of the 
system and discover potential risks and fragile points in the 
system, thereby exerting the operating potential of the 
power grid.