We present the design of a diffractive grating structure and get the optimal parameters which can achieve more than 75％ coupling efficiency (CE) between single-mode fiber and silicon-on-insulator (SOI) waveguide through 2D finite-different time-domain (FDTD) simulation.The proposed architecture has a uniform structure with no bottom reflection element or silicon overlay.The structure,including grating couplers,adiabatic tapers and interconnection waveguides can be fabricated on the SOI waveguide with only a single electron-beam lithography (ICP) step,which is CMOS-compatible.A relatively high coupling efficiency of 47.2％ was obtained at a wavelength of 1562 nm.