In this paper, we discuss the theory research and testing methods of a grating coupler. The grating coupling efficiency of parameters and the corresponding theoretical simulation was studied systematically. Meanwhile, the coupling efficiency in theory can be improved to 76% using an optimized grating design. The fabrication of the couplers in silicon-on-insulator is focusing on ion beam method (FIB). Using the tunable NewFocus laser with an adjustable extent of 1520~1570nm as the sources, Si waveguide grating is achieved vertical coupler through coupling a single-mode fiber with the diameter of 10.4. In the experiment, when the input wavelength is 1550nm, the maximum coupling efficiency is measured approximately 31% and 1 dB bandwidth is approximately 30 nm.