Abstract: To address the problems such as decreased fuel volume and increased response delay, the oil bath heating method was used to simulate the high-temperature working environment of the fuel injector. A non-isothermal one-dimensional simulation model considering the heat transfer of the external heat source was constructed through the AMESim software. The working characteristics of the common rail fuel injector under different temperature conditions were studied, and the influence of the temperature gradient on the flow and the state of the control chamber was analyzed. The research results show that the increase in temperature has a significant impact on the fuel injection volume, fuel injection rate and fuel injection duration, and the changing trends are different under different rail pressures and pulse widths. Under low rail pressure conditions, the increase in temperature leads to a decrease in the volume of fuel injection, while under high rail pressure, it shows an increasing trend. Moreover, the reduction of fuel physical properties such as viscosity and density in a high-temperature environment will weaken the pressure relief and pressure-building capabilities of the control chamber, thereby causing the start and stop points of fuel injection to be generally delayed. Meanwhile, in a high-temperature environment, the evaporation rate of fuel increases and the particle size of the spray droplets becomes smaller, resulting in a faster momentum exchange between the spray and the air, a decrease in speed, which in turn reduces the spray penetration distance, increases the spray cone angle, and reduces the development speed of the liquid-phase spray and the oil beam area.