Longitudinal vibration of drill pipe has great influence on drill pipe failure. By the analysis on the longitudinal vibration of drill pipes within the length of 2000m with ANSYS software, the intrinsic frequency of drilling pipes with different specifications, drill collars and drilling strings with different length as well as the first 5 natural vibration modes of longitudinal vibration of drill string are obtained. The results show that the intrinsic frequency of drilling pipe is slghtly affected by the drilling pipe specifications and drill collar length, but by drill pipe length a lot.