A temperature control circuit of an oven controlled crystal oscillator (OCXO) is provided. A first and a second digital potentiometer are correspondingly arranged in a bridge circuit which outputs a voltage to an input terminal of a differential amplifier (OPAMP), wherein the resistance value of the first digital potentiometer is adjustable so as to adjust the temperature of the oven to the peak temperature of the crystal resonator, and the resistance value of the second digital potentiometer is adjustable so as to cancel the temperature gradient of the first digital potentiometer. In the temperature control circuit of OCXO, the heat generation of the heater resistor is controlled by the power transistor based on the control voltage from the differential amplifier.