According to the characteristics of ice layer drilling, from the point of view of drilling hydraulics, the effect of quality and length of drilling tool, the viscosity and density of drilling fluid and some other factors on the characteristics of drilling tool lowering speed are analyzed and tested. Through the tests on the lowering process of drilling tools, with 4 different lengths and different qualities, in 2 kinds of esters drilling fluid, it is concluded that the lowering speed of the drilling tools is inversely proportional to the length of the drilling tool, and is proportional to the quality of the drilling tool, and the lowering speed of the drilling tool decreased with the increase of the viscosity and density of the drilling fluid. The acceleration time of the drilling tool lowering is mainly related to the viscosity and density of the drilling fluid, as well as the shear rate of drilling fluid while flowing on the surface of the drilling tool.