High power 1018 nm ytterbium doped fiber laser system is constructed. Output characteristics of 1018 nm laser with the length of gain fiber, the reflectivity of fiber Bragg gratings (FBG) and the diameter of core/cladding are experimentally investigated. It is found that the laser at short wavelength will get bigger gain by reducing the length of gain fiber for ytterbium doped fiber laser, 1018 nm laser can be obtained by shortening the length of gain fiber. Increasing the fiber bragg grating reflectivity and core/cladding area ratio are available approach to suppress the amplified spontaneous emission (ASE) gain and increase the laser efficient. A record output power more than 150 W at 1018 nm is obtained through using the domestic double cladding ytterbium doped fiber, with an optical- optical conversion efficiency of 71% , the ASE is suppressed efficiently.