Abstract: The high power consumption of gallium high electron mobility transistors in radio frequency power amplifier chips results in severe self-heating effects, leading to performance degradation. To more accurately analyze the impact of self-heating effects, an effective electro-thermal coupling simulation method for device chips is proposed. By coupling the device′s electrical analysis model with the temperature analysis model, the temperature changes and corresponding current performance variations of the device are observed. The heat source is calculated based on the device′s current-voltage characteristics, and the device is treated as a heat source. The finite element method is then used to solve the heat conduction equation to obtain the temperature distribution of the chip. It is observed that the self-heating effect causes a decrease in the channel current of gallium devices, and a detailed discussion revealed that the increase in temperature leading to a reduction in mobility is the main reason for the decrease in current. The temperature distribution within the chip due to the device is examined, and comparisons with commercial software validated the feasibility and effectiveness of the chip thermal simulation.