With the rapid development of communication technology, the inevitable trend in the development of communication systems is high power, wide bandwidth, and multi-carrier technology. However, passive intermodulation generated by passive devices exists widely in the communication system. Once the intermodulation products fall into the receiving band, the whole system will be interrupted. This phenomenon restricts the development of communication systems to the direction, which is equipped with large bandwidth, large capacity, and high power. Therefore, it is necessary to focus on the suppression method of intermodulation products in practical engineering applications. This paper comprehensively analyses the signal characteristics of passive intermodulation interference in different communication scenarios, such as space communication, air-based, ship, and ground, starting from the sources and characteristics of passive intermodulation and combining with the background of 6G air, sky, land and sea integrated communication. Existing intermodulation interference suppression methods are summarised from two major aspects of passive and active interference suppression, based on traditional band planning, process optimization, and device structure optimization, and expanded to advanced suppression methods such as non-contact design, analog suppression, signal processing and machine learning suppression, which provide ideas and solutions for the subsequent resolution of intermodulation interference. Finally, the development trend of passive intermodulation interference suppression technology is summarised.