The special character of in-service inspection (ISI) period means the focus of its analysis and evaluation is different from that of equipment developing and validating periods. More thorough multi-dimensional indicator system should be considered due to that equipment is under the overall fight-support system. Meanwhile, the target of evaluation is assessing whether the equipment is capable of forming and maintaining vested ability of application, which satisfies the needs of in-service condition. Focusing on the space equipment field, evaluating objects and hierarchal structure are determined by analyzing the evaluating emphasis of certain ISI period. Modified grey analytic hierarchy process is presented through comprehensive fusion of analytic hierarchy process and grey relationship analysis based on overall comparison of multiple algorisms and methods. The shortages of redundant calculation and strong subjectivity of AHP and GRA respective are avoided and overcome. The overall evaluation model is constructed and applied, which realize the comprehensive evaluation of ISI period of space equipment.