Abstract: It is believed that the temperature of air compressed by fan is higher than the freezing point, therefore the compressor would not freeze. However, researchers found in several engine thrust loss accidents occurred in recent years that the ice crystal can lead to compressor icing. The researchers have reproduced this phenomenon in the lab. Ice crystal icing research in the area of aero-engine has just started in China. In this paper, the ice crystal icing issues are analyzed and discussed from both numerical research and experimental research aspects. The highlight and limitation are also included. The research focus which should be paid attention to is proposed in the end. This paper can give some reference for engine icing study and certification.