Abstract: Thermal mass flow sensor has obvious advantages in the field of micro-flow measurement because of its simple structure and no mechanical moving parts. As far as the field of micro gas flow measuring capillary pipeline and its internal gas fluid is concerned,thermodynamics and hydrodynamics theoretical analysis were carried out. Combined with the signal processing circuit analysis,the method to eliminate the influence of environmental temperature was proposed. At the same time,the relationship between gas mass flow and temperature field of the capillary pipeline has been obtained by MATLAB language and numerical calculation,and furthermore,the transfer function about the dynamic characteristics of the thermal flow sensor was deduced,the sensor performances with different configuration modes under micro-flow conditions were simulated and tested,and the valuable results have been acquired.