The effectiveness evaluation of fighter′s infrared countermeasure is the key of operational use of weapon equipment. In allusion to simple infrared environment, fixed operational situation and single component, traditional effectiveness evaluation methods are researched, which can′t fully reflect the authenticity and exhaustiveness of infrared countermeasure. So the effectiveness evaluation method of fighter′s infrared countermeasure was put forward. The process of infrared countermeasure that was divided into three phases was studied in accordance with actual countermeasure process, such as detecting target phase, occupying phase, and killing target phase. The probability weights of different phases were confirmed based on probability methodology. And an effectiveness evaluation method based on infrared countermeasure whole process was proposed. At last, the success probabilities of accomplishing fighter′s infrared countermeasure mission were obtained. Comparisons show that the effectiveness evaluation of infrared countermeasure is valid and correct, which can provide theoretical basis for infrared attacking strategy and infrared defensing strategy.