The gradient-index strip waveguide coupler is introduced in this paper. Its principle and configuration were analyzed carefully and design equations were set up. Because a SOA's mode-dimension and emission-angle could be converted with a selected direction by a gradient-index strip waveguide coupler, a high-efficient fiber-chip coupling application was realized,and the minimum coupling loss was less than 3 dB.The graded index strip waveguide coupler could be used to replace a cylindrical lens sometimes due to their equivalent optical properties.