Herein, the lidar echo coherence was examined to investigate a reliable lidar echo processing technique and research the impact of the atmosphere on the echo phase. By creating an experimental system and developing a time domain model of the lidar, the experimental and simulated atmospheric echoes were first obtained. Moreover, the phase of the experimental echo was retrieved and aligned between pulses to remove system-error interference. Then, the correlation coefficients of the simulated echo and aligned experimental echo were evaluated based on the normalized covariance function; it is discovered that the echo pulses are incoherent. According to the evidence of the high eigencoherence of the outgoing pulse, the interpulse accumulation of the hard target echo can increase the eigenfrequency; whereas, the effect of accumulating the aligned wind field echoes among pulses is significantly worse than the incoherent average, demonstrating that the diffuse reflection of the hard target can maintain the eigensignal coherence, while the coherence of the soft target echo, such as the wind field, is seriously destroyed.