Abstract: Nonlinear buckling of flexible drill strings with weight in slant wells belongs to a research category of strong nonlinear problems.Since the Newton-Raphson method is generally valid only for weakly nonlinear problems and hard to meet computational accuracy and reliability requirements of engineering projects,a four-order nonlinear equilibrium differential equation of drill strings expressed by cylindrical coordinates could be numerically solved directly by the differential quadrature element method,and an incremental iteration method was constituted using the arc-length method with DQ elements.Two engineering examples were given to validate the efficiency of this method.The numerical results indicated that the DQ element method could overcome difficulties encountered in dealing with the drill-string weight by the finite element method,and the solution accuracy was significantly improved.Numerical examples revealed that the arc-length iteration method based on DQ elements was characterized by being simple,easy to use,good in convergence,and able to accurately capture the critical load of helical buckling.Therefore,this method can be used readily for the nonlinear buckling analysis of drill strings in slant wells.