Air lift reverse circulation drilling technology has been widely used in the field due to its high drilling efficiency， simple process， cleanliness of the hole. However， the design of the dual wall drill tool mainly relies on the experience， and immature theoretical research leads to the lack of in-depth analysis of the problems in the field. In this paper， the velocity and pressure characteristics of the flow fields in the dual-wall drill rod annulus and the air-water mixer in air-lift reverse circulation technology are simulated by means of the numerical simulation method. Flow field analysis results show that reducing diameter changes in the annulus or increase the length with the diameter change is more advantageous to reduce the pressure loss and energy loss along the dual-wall drill rod， and the completely symmetrical air inlet structure of the air-water mixer is more advantageous to the evenness of the up-hole velocity， and reduces the occurrence of blockage. The results of the study can and provide reference for design of gas lift reverse circulation drilling tools， and solutions to field problems.