The failure modes of electric squib were studied during accelerated life test. The conditions of the aging test were temperature 71 ℃ and temperature 71 ℃, relative humidity 50% and 80%. The results show that the resistanc, fire time and output gass pressure did not change obviously, but the breakdown voltage dropped after accelerated life test. Especially, in the condition of humidity, the breakdown voltage of electric squib dropped significantly. By studying the effect factor to electric squib′s breakdown voltage, the reason was the inhomogeneous mixing of epoxy resin at the condition of humidity.