This paper studied the principles of thermal gas mass flow meter. According to the car engine EGR cooler working principle, we found out a kind of heat dissipation gas mass flow meter to measure the mass flow quantity of the gas in the EGR cooler test and analysis system which is a newly applied invention patent. We analyzed various parameters of the gas mass flow meter suitable to the system. Meanwhile, in order to verify reliability of the thermal gas mass flow meter in the system, we adopted CFD method to simulate the EGR cooler by using empirical parameters, and collected several related sensor parameters of the EGR cooler in the condition that the inlet temperature was constantly at 368K while the coolant had 4 kinds of degrees. Combining heat empirical formula, we got the EGR cooler outlet temperature and the overall heat transfer coefficient. After comparing the calculated values of the gas path total EGR cooler outlet temperature and heat transfer coefficients with the experimental values, we found that the outlet temperature values of experiment were smaller than the calculated values by averagely 1.17%, while the average experimental values of the overall heat transfer coefficient were 3.1% larger than the calculated values. Thus, this type of mass flow meter has good stability in the newly applied Chinese patent EGR cooler performance test and analysis system.