An optimum grid pattern of the concentrator solar cell top contact metallization was designed. Several power-loss mechanisms of the smallest element were analyzed detailedly. The optimum grid spacing recursion formula was deduced. The optimum grid spacing and the power-loss for the grids of different width were calculated. The shadowing loss was the biggest loss when the grid spacing was narrower than the optimum one if ohmic contact was very well. Otherwise,the current transporting power losses of the grid and solar cell material became the main reason. For the high concentrator solar cell,the thickness of the grid was proposed to be designed more thickly. The results of calculation and analysis can be used in the designing concentrator solar cells.