The EUV imager is used to observe the 30.4 nm radiation of the earth's plasmasphere on the lunar surface. The 30.4 nm multilayer is the key optical part of the imager. According to the technical parameters, the B4 C/Mg, B4 C/Mg2Si, B4 C/Al, B4 C/Si, Mo/Si and so on were chosen. The period thickness, ratio of the material and the number of the periods were optimized and the reflectivity of those multilayers were calculated. In consideration of the lunar environment, the Mo/Si and the B4 C/Si multilayer were deposited by magnetron sputtering coating plant. The reflectivity of Mo/Si and B4 C/Si multilayer at 30.4 nm is 15.3% and 22.8% respectively.