The echo signals have a large dynamic range in the applications of photon counting mode lidar. The far-field echo signals of lidar are within the linear output range of detectors and thus no calibration is required. However, because the near-field signals are usually within the non-linear response area of detectors,it is necessary to calibrate the near-field signals. In order to improve the signal-to-noise ratio of far-field signals, a novel calibration method is proposed. According to the pulsed lidar equation, the corrected near-field signals are obtained by the retrieval of the far-field signals, and simultaneously are compared with the received echo signals to obtain a calibration factor. The data before and after correction by this calibration factor are further used to retrieve the visibility, respectively, which is compared with the detection results obtained by the visibility sensor. The results show that, for the uncorrected data, the average deviation and standard deviation between the visibility obtained by the far-field signals and that by the visibility sensor are 0.57 km and 1.89 km, respectively, while the average deviation exceeds 10 km for the near-field signals. The visibility obtained from the corrected data is in a good agreement with that by the visibility sensor. The average deviation and standard deviation are 0.43 km and 0.76 km, respectively.