In the temperature control system,the thermistor is an important element.The temperature characteristic of themistor shows to be nonlinear,thereby the output ofthermistor circuit is characterized by nonlinearity,which has influence on the measuringaccurancy. In order to improve the nonlinear charactoric,the compensation resistance isadded in the circuit.The determination of resistance value has direct influence on the com-pensating results.Therefore,the conjugate gradient method is adopted to conduct the opti-mization processlng.