Abstract: To improve the imaging quality of lens used in the helmetmounted LLL nightvision system and make lens small in size, light in weight, the lens with the high order aspheric surface is designed. According to the theory of the aberration, the lens of the helmetmounted nightvision imaging system is designed to meet the demand. When spatial frequency is 40lp/mm, onaxis MTF can reach 0.62 and offaxis MTF 0.42. On the other hand, its total weight is about 300g，the number of lens is reduced from 9 to 6, the total length of the system from 81mm to 72mm. The analyzed results show that the construction of the aspheric surface for helmetmounted LLL nightvision systems can make its lens configuration simple.