The invention discloses a power system load modelling method, including the steps that: A, load classification based on daily active load curve; B, load modelling based on statistic synthesis method; C, load model parameter sensitivity analysis and range analysis based on simulation analysis; D, load model parameter node identification based on genetic algorithm, namely node identification is carried out by taking fitted local disturbance data as target, setting low sensitivity parameter value as statistic synthesis method surveying parameter value and adopting the genetic algorithm, so as to obtain multiple groups of load model parameters; E, load model parameter wide area check based on WAMS, namely load model parameter check is carried out by taking the multiple groups of solutions identified by node as initial value and taking accurate fitting on system wide area dynamic characteristic as target, so as to obtain unique solution capable of reflecting wide area dynamic characteristic when system is subject to disturbance. The invention solves the problems of multiple solutions and identifiability of overall measuring identifying method by load point classification and load model parameter aggregation and has popularization and application values.