The pressure, flow, and temperature of reactants play a crucial role in the operation of the proton exchange membrane fuel cell (PEMFC), directly impacting its performance. To accurately assess the stack output characteristics, precise regulation of the inlet gas temperature (air and hydrogen) is essential. This study proposes a control structure for maintaining the temperature of the inlet-stack gas. The primary actuators employed in this control structure are the heating belt and solid-state relay. An adaptive PI controller is designed based on self-regulation of the temperature error. The controller's output is mathematically converted into a PWM signal, enabling it to act on the actuators. To validate the feasibility of the control structure and controller, mathematical simulations are performed using MATLAB/Simulink®. Subsequently, experimental validations are conducted on a PEMFC stack test bench. These validations encompass step test, robustness test, and operational stability test. The step test results reveal that the average rise rate of the inlet air temperature is approximately 6.78°C/min@265NLPM, with the temperature increasing from 19.1°C to 75.6°C in 500 seconds. The inlet air temperature exhibits no overshoot, and the maximum steady-state fluctuation is approximately ±0.6°C. The robustness test demonstrates that the designed controller exhibits good resilience to large step changes in flow rate (70-140-350NLPM) and set temperature (40-70°C). Additionally, an 8hour and 20-minute continuous experiment is conducted to assess the reliability of the control structure during long-term operation. The maximum absolute error value observed in the inlet air temperature during this test is 0.7°C, highlighting the excellent reliability and accuracy of the control structure and controller.