The effect of micro-hotplate (MHP) thermal deformation on the signal output of the MHP-based micro gas pressure sensor is investigated. Combining electro-thermal theoretical analysis and thermal-mechanical finite element modeling, different electro-thermal-mechanical analysis models of the sensors are built and solved at constant current condition and constant temperature condition respectively. The calculated results show that the MHP thermal deformation has little effect on the sensor signal output over the entire pressure range at constant current condition, I=0.7mA. While at constant temperature condition, Ts=400K, thermal deformation has little effect on the sensor signal output at low gas pressure, but at high pressure the effect are great. Moreover, according to the thermal-mechanical analysis, we find that optimizing thickness distribution of thin films in the MHP suspended structure can reduce thermal deformation effectively at higher temperature when the lateral dimension is same, which presents a practicable method to improve the sensor stability.