A Surface Plasmon Resonance (SPR) sensor is tested precisely with the prism angular detection approach. The working principle about the temperature effect on SPR is theoretically analyzed, and then the testing system is designed according to the principle. The thermal effect on the resonance angle of SPR was investigated based on angular detection. The experiment result proves that the SPR angle descends with the increase of temperature. Moreover, the slope is about -7.843×10^-3/℃. It shows that the temperature control is important in the practical application of the SPR sensor.