To measure the characteristics of a target in a complex environment is extremely difficult. The components and features of a complex infrared environment are studied. The influence of the complex environment on the measurement of infrared characteristics of a target is analyzed systematically. The measurement condition and requirements are proposed. Finally, the methods for measuring and studying the infrared characteristics of a target in a complex environment are discussed in detail. The result is of referential value to the measurement and study of the radiation characteristics of targets.