According to the difficult problems of the smoking screen for camouflage in large area,a new passive jamming method,which can make fog through compound of producing fog,has been put forward.The micro principle of artifical fog was discussed.The micro physical characteristic and photoelectric jamming of fog,which is in different temperature and relative humidity,were investigated.The results show that the fog with high water content has good photoelectric property for obscuring at low temperature and high relative humidity.When the visibility of fog is below 1m,the fog has good obscure effect for the target in 25m,and the target in 40m can't be distinguished from the surroundings on the infrared image.