A two rings, triangular lattice photonic crystal fiber sensor element using surface plasma resonance phenomenon is proposed. The performance of the sensor is analyzed by finite element (FEM) analysis software Multiphysics COMSOL. The influence of structural parameters on the performance of the sensor is discussed. The results show that the maximum sensitivity is 6000nm/RIU, when refractive index is in the range of 1.31 to 1.38. The sensor can be directly placed in the liquid and platinum layer is placed outer surface of the photonic crystal fiber, which can simplify the manufacturing process and the measurement process , has important practical value.