Due to the limitation of a lidar’s field of view, the near-field signals cannot be completely received by telescopes as receiving atmospheric echo signals. This is negative for a Raman lidar which focuses its detection area on the troposphere. The geometric factor was introduced to the lidar equation and was detailed theoretically analyzed in the view of geometrical optics. For comparison, ray tracing method was also used to solve the overlap problem. They turn out a high degree of coincidence. In order to improve the efficiency of receiving near-field echo signals of a fiber-coupled Raman lidar, the effect of the optical fiber in the axial and lateral displacement was researched. In addition, the method of lateral shifted fiber and the laser axis inclination are proved the same influence in receiving the near field echo signals. The results are especially meaningful for a smaller FOV Raman lidar system.