Abstract: Low-level-light night-vision system is an important equipment of sight and navigation for pilot. Objective lens is an important part of the low-level-light night-vision system. An all-sphere objective lens was designed based on a six elements initial lens, then a modified system of plastic lens with hybrid refractive/diffractive and freeform surfaces was developed. The optimization process was also presented. The performance of the couple systems were presented and analysed. It is shown that the modified system not only has better performance, for example lateral color, distortion, astigmatic and modulate transfer function (MTF), but also has greatly improved in weight, total length and max diameter, which can meet the demands of night-vision objective lens. It also provides a new approach for modern lightweight and compact low-level-light night-vision system design.