Helicopters are widely used on the battlefield owing to their advantages of vertical take-off and landing,hovering in the air,and flying close to the ground.However,in degraded vision environmentsthe helicopter pilot's vision capability is limited and it is difficult for the pilot to observe the environment outside the cabin,which may lead to the occurrence of accidents.The airborne vision system can effectively solve this problem through the steps of sensor detection,data processing and terminal display.The directions of research and development of the vision system in degraded vision environments are sorted out,the capabilities of the vision system oriented to degraded vision environments are analyzed,and the principles,advantages and problems of different levels of vision systems are illustrated,which have certain reference value for the development of the airborne vision system onboard a helicopter.