In order to study the changes of the atmospheric boundary layer’s structure in Hefei, the polarization-Raman-Mie scattering lidar system is operated automatically and continuously. The gradient method used to extract the height of atmospheric boundary layer from lidar data is introduced and analyzed. The modified gradient method is used to obtain the temporal characteristics of the height of atmospheric boundary layer in Hefei. The results show that the height of atmospheric boundary layer in Hefei ranges from 1 km to 1.5 km, and the average height is about (1.28±0.2) km during the experiment.