Abstract: This paper analyzes the stress feature of sucker rod string in a horizontal well,and discusses the necessity of weighting rod in horizontal.The method for calculating the axial force,bending moment and bending deflection sucker rod string with centralizer is obtained applying compressional-to-shear buckling continuous beam-string theory-The design method for sucker rod string with weighting rod is presented in this paper,which takes the modified Goodman stress diagram as strength design principle and considers the rigid conditions of rod string.A practical example is used to show its application method.