As an important part in power systems， the load is given attention because the accuracy of its model will affect the results of analysis to a great extent. The load area modeling， network simplification and load model parameter identification are studied by using the synchronous data. The concept of the aggregate load area model（ALAM） based on the power system wide area measurement system is proposed. The parameter identifiability regarding the ALAM is studied. As a result， the network model of ALAM is determined and guidance for the area load modeling is given. A simple power system is used as an example， with the effectiveness of the load modeling method proposed verified by the simulation results.