The invention discloses a load dynamic modeling method considering the time-varying composition of AC/DC distribution network load. The technical scheme adopted by the invention is as follows: step 1,approximately decoupling a DC distribution network into a DC inverter power source; 2, carrying out simplification and equivalence on each load composition of that DC distribution network, and further establishing a generalized comprehensive load equivalence model of the PCC point; 3, clustering that historical data and performing training by using the classifier; 4, identifying the fault data recorded by the fault recorder by the overall measurement and discrimination method, and establishing a model parameter library according to the identified result; 5, designating that required simulation scene, and selecte a priori model parameters according to the classification result. The invention considers the parameter selection problem of each load composition of AC/DC distribution network intransient simulation under different time-varying scenarios, further improves a more reliable dynamic load model for transient simulation at the transmission network level, and makes a great step forward in the universality of the generalized load model under high-proportion renewable energy sources.