Abstract: In high-angle long horizontal wells, the length of the horizontal well section is longer than that of ordinary wells. With the increasing contact area between the tubing and the sidewall, the friction resistance gradually increases, which leads to the “self-locking” phenomenon of the tubing, making it difficult to run the tubing into the predetermined well depth, which seriously limits the development efficiency of oil and gas wells. In order to solve this problem, this paper fully considers the geometric parameters of borehole, tubing stiffness and buckling, analyzes the stress of tubing in different buckling states, establishes the mechanical models of tubing in three buckling states, and studies the running-in performance of tubing by using the safety factor method combined with the fourth strength theory. Using MATLAB analysis software, the relationship between pipe diameter, friction coefficient and tubing running ability is studied. The results show that 2\dfrac78 outer thickened tubing can run to the specified well depth when the friction coefficient is 0.2. The stress of the oil pipe is checked by using the safety factor method combined with the fourth strength theory, and the numerical calculation results are consistent with the analysis results.