Abstract: In this Paper,some methods,such as data fit,cubic spline and data integration.are used to describle the trajectory of horizontal well.That can provide conditions for the finite element analysis meanwhile,the internal force that will cause of the easing initial buckling is calculated in horizontal wells with the method of Tri-moment formulate.It has been proven that the method is applicable and reliable through the analysis of the case history and will be useful in guiding drilling operation.