In this paper,we propose two kinds of composite structures based on the one-and two-dimensional (1D&2D) gold grating on a gold film for plasmonic refractive index sensing.The resonance modes and sensing characteristics of the composite structures are numerically simulated by the finite-difference time-domain method.The composite structure of the 1D gold semi-cylinder grating and gold film is analyzed first,and the optimized parameters of the grating period are obtained.The sensitivity and figure of merit (FOM) can reach 660 RIU/nm and 169 RIU-1,respectively.Then,we replace the 1D grating with the 2D gold semi-sphere particles array and find that the 2D grating composite structure can excite strong surface plasmon resonance intensity in a wider period range.The sensitivity and FOM of the improved composite structure can reach 985RIU/nm and 298 RIU-1,respectively.At last,the comparison results of the sensing performance of the two structures are discussed.The proposed structures can be used for bio-chemical refractive index sensing.