Based on the rate equation model of end pumped alkali vapor laser, the characteristics of alkali vapor laser in different buffer gas environments were studied. The temperature vs output power of alkali vapor laser in different gas environments were obtained by optimizing the parameters of output coupler reflectivity and gas pressure. Results show that the optimal output power and operating temperature are improved and decreased with the increase of mixing rate in hydrocarbon DPAL respectively. And the optimal operation states of hydrocarbon DPAL can be described by its quasi two level operation curve. Moreover, the helium pressure in hydrocarbon free DPAL can be reduced largely by using 3He gas. Besides by using 3He gas, the output power can be improved for hydrocarbon free Rb-DPAL but not for hydrocarbon free K-DPAL. The simulated results have a good matching with reported experimental results, which will supply significant reference for further experimental research.