Temperature and pressure as two important working conditions of the air ejector are very important to its working performance. Taking the air ejector installed in a power plant as an example, and using ANSYS-FLUENT software, the three-dimensional simulation of the operation of the air ejector under different pressure and temperature conditions is carried out, and the relations between pressure, temperature, inlet gas flow rate and ejection coefficient are given. The results show that the working conditions of pressure and temperature have some influence on the performance of the air ejector. It is important to control the working conditions of the air ejector.