In chemical oxygen-iodine laser (COIL), the near-resonant energy transfer reaction between O2(1Δ2) and I is a process of heat release, which is harmful to the stimulated emission as the heat release reaction caused by vapor quenching and unaviodable. The influence of quenching heat release on pneumatic properties of resonator and output power is calculated. The magnitude of near-resonant energy transfer is related to the population inversion and stimulated emission, in other words, is proportional to the gain of resonator and intensity distribution of laser, so this effect mainly occurs at the front part of the entrance of resonator. The effects almost are equivalent to the quenching by 7% H2O population influencing on chemical oxygen-iodine laser, and the theoretical model for chemical oxygen-iodine laser is improved.