Aiming at the problems of low coupling efficiency, large polarization related loss and complex structure of two-dimensional grating couplers, a new two-dimensional grating coupler based on silicon on insulator(SOI) material applied in C band is proposed. The coupler is composed of four hole staggered rhombic etching cell unit cycle arrangement with a 45° incli-nation angle. The period, etching depth, relative position and radius of etching circular hole of the coupler are optimized by using inclined coupling mode, and conduct simulation verification on it. The simulation results show that the coupling loss of the coup-ler is as low as -2.4 dB at 1 540 nm, the polarization related loss at C band is less than 0.2 dB, and the 1 dB and 3 dB operating bandwidths are 36 dB and 58 nm respectively.