Abstract: Flexible drilling tools are widely used in ultra-short radius horizontal wells, and their structural parameters have a significant impact on the load transmitted to the drill bit. The flexible drilling tools of ultra-short radius horizontal wells are thusly taken as the research object, and the finite element method is adopted as the analysis tool. Based on its structural and force characteristics, a flexible drilling tool and wellbore wall multi-layer contact nonlinear model and a numerical calculation method are proposed, which can describe the multi-segment hinged characteristics of the inner flexible drilling string, the structural discontinuity characteristics of the outer guide tube, and the double-layer contact nonlinear characteristics between the inner-middle-outer layer structures. The effects of single section length and hinged limit degree on mechanical behavior of drilling tools and load transmitted to the drill bit are analyzed. The results show that: with the increase of the single section length of the flexible drilling string, the torque transmitted to the drill bit first decreases and then increases, while the bit weight on bit changes randomly. The maximum loss rate of bit weight on bit is 68.7%. With the increase of the hinged limit degree of the flexible drilling string, both the torque and weight on bit transmitted to the drill bit gradually decrease. This study can provide a reference for the structural optimization design of flexible drilling tools.