The force on the drill string is very complex in the process of drilling direction wells. A merely drill string vibration includes longitudinal vibration, transverse vibration and torsional vibration, of which longitudinal vibration is one of the major factors leading to drill string failure. Therefore, the longitudinal vibration of direction wells is needed to further study. In this paper, the regularity of longitudinal vibration was analyzed by using finite element method. Firstly, according to the characteristics of direction wells, a whole-well drill string model was established, then with the drill string module as an object of study, a whole-well drill string mechanical model of longitudinal vibration was established. Through analysis of the computer by means of linear algebra, the regular distribution of longitudinal vibration resonant frequency of direction wells was obtained. The resonant frequency of drill string longitudinal vibration depends upon material properties of drill string and morphological characteristics, but has little to do with the length of the drill string. In the longitudinal resonance state, drill string comes into intense collision with the wall, which will cause serious damage on drill string in a short time. At the same time even give rise to borehole collapse, result in economic loss to the drilling operation. It is very significant that the study of this issue can be used to direct drilling operation and reduce accidents such as bit bounce, drill string failure and so on.