The invention discloses a method for evaluating the 
electric power system risk based on fault pre-scanning. The method comprises the steps that firstly, according to the current structure of an 
electric power system and a planning scheme, a corresponding planning scheme model is established; secondly, based on device data and a 
power grid structure, predicted faults and the possibility of the predicated faults of a 
power grid are analyzed, and then a pre-scanning fault set is formed; thirdly, through the risk state based on direct-current 
power flow, screening and ordering are conducted on the predicated fault set, so that a fault state 
list is formed; fourthly, all 
power flow corresponding to the faults in the 
list is worked out, and for the fault with the 
power flow out of range, the consequence of the fault is 
load loss; fifthly, according to the 
load loss of the fault states and the possibility of the fault states, the 
system risk indicator is worked out; sixthly, according to the 
system risk indicator, the system weak link is found out. By the adoption of the method for the evaluating 
electric power system risk based on fault pre-scanning, analysis of all the fault sates in the fault set through alternating-current power flow is avoided, so that the calculation amount of follow-up alternating-current power flow analysis and 
risk indicator processing is greatly reduced, and a large 
mount of calculation time is saved.