The coupling of laser with fiber has been used for many fields: such as industry, medical treatment, and communications. At the present time, the coupling methods are direct coupling and lens coupling mainly. With the existence of a damage threshold in fiber end face and interior, it very difficult to use the above ways to realize the coupling of high-power, high-energy and narrow pulse laser with optical fiber. In this paper, a new method to reducing laser power density and energy density in optical fiber end face and interior is presented and designed a hollow cone shaped laser-fiber coupler by analyzing the mechanism of damage of optical fiber. When cylindrical Gauss beam incident into the hollow cone coupler will form a light spot, the energy density is of quasiaverage distribution. By using this coupler, we realized the coupling of a high-power (10MW), energy (12mJ), narrow pulse (12ns) and electro-optical Q-switched Nd:YAG laser with the multimode optical fiber (diameter is 600μm) and the coupling efficiency is 70%.