Abstract: Thermal expansion actuated characteristics of paraffin were tested on apparatus heated by water bath and the relationship of volume expansion vs.temperature and pressure,the influence of pressure on thermal expansion characteristics,and the melting point of binary paraffin mixture were studied.The results indicate that the volume expansion coefficient of paraffin increases and reach 13.2% with the temperature changing from 25 ℃ to 61 ℃ and the pressure below 0.36 MPa,and the characteristic curve is almost linear during the solid-to-liquid phase transformation.The influence of pressure on thermal expansion characteristics of paraffin is very little under the used pressure of spring.The paraffin with different melting points can be selected as the expansive material of paraffin actuator according to the demand of control system.