A fast algorithm based on the boundary of laser beam is proposed. Based on the time-space distribution of laser radar signals, the response function of the detection target to the signal and the model of the interaction process between them are deduced and established. A target reconstruction simulation system based on the laser reflection tomography is constructed. Based on the influences of the different sampling intervals and the different detection angles on the reconstructed image quality, two sets of comparative simulation experiments are carried out. Under different conditions, the filter backprojection algorithm is used to achieve the image reconstruction of the two-dimensional contour for the target.