The return signal statistical model of differential absorption lidar (DIAL) is the basis of studying differential absorption lidar. However, the known statistical models ignored the effect of laser scintillation resulting from atmospheric turbulence on return signal. With considering effects of laser scintillation resulting from atmospheric turbulence, target reflective speckle, receiving noise and the fluctuation of transmitted power, a revised return signal statistical model of long-range DIAL is presented and the statistical characteristics of this model are analyzed. The simulation results show that laser scintillation resulting from atmospheric turbulence has an important effect on the statistical characteristics of return signal and verify this statistical model more accurate and reasonable than other known models.