Abstract: The investigation and study on the overall process of tubing lowering in Well LG351 are carried out. The results of the said investigation and study, and also relevant field application show that thread galling or wrong make-up easily occurs, if the guiding screw operation fails to make the threads in place, and that thread galling also occurs with high probability in case of improper make-up control method or over torque. In order to ensure successful tubing lowering operation,relevant operation and maintenance procedures for tubing running shall be strictly followed with focus on such aspects as protecting,cleaning,inspecting,and repairing of the thread connection,compound applying,thread stabbing,guiding screw, making-up,and make-up speed and torque control as well as make-up control method.