Manual calibration is often used in the luminance thermometer, which exists a high influential artificial factor and a low repeat ability of calibration. In order to make the thermometer accurately and automatically aim at the aiming point of the lamp, double degree of freedom automatic aiming system is designed. The YG-QP36 four quadrants detector was chosen as the photoelectric detector. The mechanical structure of automatic aiming system is designed, and the stepper motor has the characteristic of self-locking and two-way accurate location, which can scan the aiming point of the lamp in two degree of freedom. The optical fiber can isolate electronic components from high temperature environment, which reduces the temperature influence on electronic components. The temperature-voltage data was collected in 800~1 200℃, and the data was fitted with the least squares support vector machine. The relative error is less than 0.05%, the reconstruction of mean square error is 0.019 6. The least squares fitting between the distance of the flare of the circle to the origin of coordinates and voltage was made. The spot diameter was measured, experiment results show that the double degree of freedom automatic aiming system can improve the accuracy of calibration, and reduce the repeated calibration error.