In order to meet the application needs of unmanned driving and vehicle obstacle avoidance, imaging lidar usually needs to identify target signals in a large dynamic range of several meters to several hundred meters. Limited by volume and cost, lidar usually does not have automatic gain control function. Therefore, high precision measurement of saturated to unsaturated echo signals is one of the problems that imaging lidar needs to solve. Traditional imaging lidars mostly use the TDC method. This method is effective for the saturated waveforms of the targets nearby, but has limited imaging ability for unsaturated echo signals far away. Therefore, a method of full waveform matching based on high speed ADC was proposed. The high-precision peak position of the echo pulse was obtained by sliding matching the echo pulse and the template waveform. And an optimized fast algorithm on FPGA was implemented, which improved the execution speed. The accuracy of ranging was ensured and the effective imaging range of the imaging lidar was increased. Through a large number of experiments, the imaging lidar has a ranging accuracy of 2.7 cm and an effective imaging range of more than 200 meters.