To evaluate the reliability of laser diode initiation(LDI) subsystem at low temperature, the performances of a dual-way LDI subsystem and its individual parts were studied by temperature test and initiation test. Based on sensitivity tests of laser initiators, 99.9% firing laser energy at 95% confidence level was estimated as 0.783 mJ at 20 ℃ and 0.747 mJ at -40 ℃. The characteristics of semiconductor laser and optical transmission efficiencies were studied at -40-20 ℃ and a numerical fitting empirical formula was obtained via analysis. The value of firing energy to each laser initiator was calculated and obtained using the fitting formula and the ignition margin of the LDI subsystem obtained is more than 3. Through low temperature firing test, it is verified that the dual-way LDI subsystem can be normally fired, having a higher design margin.