Aiming at the problems of low sensitivity and complex structure of surface plasmon polariton(SPP) sensor at the present stage, a highly sensitive and tunable SPP sensor composed of metal-insulator-metal waveguide and a resonant cavity embedded with silver nanorods is proposed. The optical transmission characteristics and sensing characteristics of the designed sensor are studied by using the finite difference time domain method. The simulation results show that the transmission spectrum will show four or two resonance peaks in the wavelength range of 500~3500 nm when the silver nanorods are introduced into the resonator cavity or not. The refractive index sensitivity of the structure is as high as 2116.72 nm/RIU, the quality factor is 27.51. By filling the cavity with ethanol, the structure can measure the ambient temperature, and the temperature sensitivity can reach 0.98 nm/℃.