With the characteristics of high sensitivity and small volume, photon counting radar represents the future development trend of long-range detection radar. But photon counting radar in the detection will produce range walk error, thus affecting the ranging accuracy of the system. In this paper, the relationship between the range walk error and the detectors timing jitter is theoretically analyzed and experimentally verified. First, based on the lidar equation, timing jitter of single-photon detector and probabilistic statistical properties of photon counting detection, a mathematical model of the echo signal and detector timing jitter was established. Then the model was used to further derive the detectors timing jitter and range walk error. Computational analysis and simulation experiments show that the range walk error of the system is positively correlated with the timing jitter of the detector. Finally, experiments were conducted using single-photon detectors with different timing jitter, and the results show that when the standard deviation of the detector time jitter is 15, 350 and 1152ps, the walk error is 0.88, 2.55 and 12.56cm, respectively.