Abstract: Downhole drag and torque are two key factors which affect design and operation of extended reach well.In this paper,the loaded state of tubular element in three dimension wellbore was analyzed,the general numerical model and arithmetic for downhole drag and torque calculation were set up,and numerical calculation software was developed.This software had been applied successfully to case analysis of drilling and casing running operations forXijiang extended reach wells in South-China Sea.The numerical simulation and predictive analysis on downhole drag and torque were made with this software,and satisfied results were obtained.Consequently,it can be generally applied to future extended reach well engineering.