In order to reduce the problems probably happened when carrying out the on site test of UHV 1100 kV GIS, and based on the on site experience of domestic UHV substation test in recent years, the test technology of on site AC voltage test of UHV 1100 kV GIS is systematically introduced in terms of the structure characteristics of UHV 1100 kV GIS, the choice of test scheme, consideration of test frequency and voltage applied process, attentions of test wiring, and test criterion. This paper also analyzes the key points during the test in detail, and gives an estimated example of test parameters which provides the basis for equipment configuration and test source choice. Adequate preparation should be made ahead of time due to high AC withstand test voltage of 1100 kV GIS, large capacity of equipment, great height of bushing, which may bring many difficulties to the actual implementation of on site test.