Abstract: Study of the method of solar energy resource assessment is a basic work for the development and utilizing of solar energy. A lot of researches about this work have been carried out since 1950s. In this paper, we summarize previous works and partitionthem into 2 kinds, which are statistical method and physical method. Parameters in every method are introduced and the strongpoint and shortcoming about every method are commented. Difficulties and emphases in current solar energy resource assessment are analyzed and discussed. It is considered that the calculations of the influences of cloud and aerosol on surface radiation are two difficulties. Development should be focused on integrative method including all kinds of data in the future.