The invention belongs to the technical field of online monitoring and evaluation of insulation statuses of a gas insulated switchgear (GIS), and particularly relates to a method for comprehensively evaluating the insulation status of the gas insulated switchgear (GIS). The method mainly comprises the steps of GIS insulation status evaluation index system framework construction, GIS insulation evaluation index weight calculation, GIS insulation status partition based on a fuzzy theory, and multi-source status evaluation mathematical model fusion based on an evidence theory. The method involves evaluation indexes, is comprehensive and reliable in evaluation model, has simple and clear evaluation results, and can be popularized and applied to actual engineering fields. In consideration of limited running condition of the GIS, a comprehensive index system reflecting the insulation status of equipment can be constructed by using complementary information under different monitoring conditions, and the fuzzy theory and a data fusing theory are introduced in conjunction with expert experience, so that comprehensive evaluation of the insulation status of the GIS equipment is realized, and a comprehensive and reliable scheme is provided for multi-source information evaluation of the same type of equipment.