Temperature sensor system based on surface acoustic wave resonator (SAWR) is passive and wireless which can be used in substation equipment,such as switchgear.The interrogation unit is assembled with discrete components.The direct digital synthesizer(DDS) mixed with the local oscillator was adopted in RF transmitter chain circuit for satisfying fast frequency changing.The double heterodyne downconversion was adopted in RF receiver chain for decreasing noise from transmitting.The timing of transmit and receive was exactly controlled for improving the measure precision and distance.Testing data form the sensors at -40～90 ℃ circumstance was analyzed, giving the temperature precision of ±1 ℃.In good electromagnetic circumstance, the maxim measure distance could reach to 1.5 m.