In this study, the instability phenomenon of an infrared trigger device that has operated for a long period of time is examined on the basis of working principle of the device and by means of experimental monitoring and analysis. The threshold current, $I_{\mathrm{t}\mathrm{h}}(T)$, of the infrared laser, which is the source of the infrared laser triggering device, increases after the infrared trigger device works for a long time owing to heat accumulation. In contrast, the output current, $I_{\mathrm{o}\mathrm{u}\mathrm{t}}(T)$, of the constant current source decreases with the increase in temperature. When $I_{\mathrm{o}\mathrm{u}\mathrm{t}}(T)<I_{\mathrm{t}\mathrm{h}}(T)$, the infrared laser cannot emit the laser normally, and the output power becomes unstable; this leads to the instability of the infrared trigger. Upon increasing the output current of the constant current source to 1.44 times the maximum threshold current, that is, beyond 640 mA to make $I_{\mathrm{o}\mathrm{u}\mathrm{t}}(T)>I_{\mathrm{t}\mathrm{h}}(T)$, the infrared laser can be guaranteed to be in a stable luminous state within the range of temperature change, and the infrared trigger device is therefore in a stable working state. After a long period of power-on operation experiment, the infrared trigger worked stably and did not trigger the signal by mistake, indicating that its instability problem is effectively addressed. The findings of this study have important engineering application value in improving the stability of infrared trigger devices.