The effect of temperature change of BBO nonlinear crystal on the photon output angle and conversion efficiency of spontaneous parametric down-conversion is studied， so as to obtain the appropriate operating temperature of BBO nonlinear crystal and reduce the influence of temperature on the long-term stability of the system. The crystal clamping and temperature control system is designed according to the experimental requirements， and the feasibility and reliability of the system are guaranteed by ANSYS thermal analysis. After that， by changing the crystal heating temperature， the relevant photon output angle and the change curve of photon number rate with temperature under different beam masses were measured under the temperature control accuracy of no less than ±0.03℃. The results show that with the increase of crystal temperature， the output angle of relevant photon decreases proportionally with the change of temperature， which is consistent with the theoretical calculation results. Meanwhile， the increase of BBO crystal temperature from 25℃ to 55℃ can increase the photon rate of poor beam quality by about 34%， and the subsequent temperature increase in a small range will greatly increase the background noise of measurement while increasing the photon rate. Based on the comprehensive results， it can be seen that the temperature used by BBO crystal in the working process should be 55℃.