Abstract: The terrestrial ecosystem carbon monitoring satellite is China′s first satellite with forestry remote sensing as its main application.The satellite is equipped with a 5-beam full waveform sampling lidar based on the pulse time-flight ranging system.In order to meet the high fidelity，large dynamic and high precision measurement of forestry，a dual-channel laser detection system with “fixed gain + variable gain” was designed.The detection system has the characteristics of high bandwidth（80MHz），high sampling rate（1.2GHz），high quantization bits（12bit），and the dynamic range covers more than 40dB to ensure the undistorted recording of the laser signal.Based on highly stable（10^-8）constant crystal oscillator，the time measuring unit achieved measuring accuracy better than 300ps through efficient waveform extraction and high-precision centroid extraction algorithm.The relative delay of dual-channel laser detection system was calibrated，and the fusion application of dual-channel data was proposed.The lidar has been running for 1 year，and the accuracy of ranging is better than 0.15m.

Key words: the terrestrial ecosystem carbon monitoring satellite, lidar, forestry, large dynamic, double gain