A parameter adaptive differential evolution algorithm was proposed to measure the diameter at breast height (DBH) of tree trunk by fitting circle. A DBH measuring platform made by laboratory was utilized to collect the data, and the Kmeans algorithm was first introduced to cluster the data and segment the background and target. In order to improve the fitting accuracy, the angle compensation method used arc length was employed to compensate the deflection angle of the trunk surface point to the laser sensor center before fitting. Then, the center of laser sensor was taken as the coordinate origin, and the horizontal and vertical coordinates of the trunk surface points were calculated. Finally, the adaptive differential evolution algorithm was proposed to fit the tree trunk surface. In the process of fitting, the number of population, evolutionary strategy, scaling factor and crossover rate of the differential evolution process were adaptively changed with the evolution process. Totally forty different sizes of trees in the campus and artificial forest were measured and fitted respectively, and the fitting time was 1.41s. The results of the proposed method were compared with the real values of DBH. The RMSE for DBH of trees in the campus and artificial forest were 4.996mm and 4.500mm, respectively. At the same time, the results were compared with the Levenberg-Marquardt (LM), particle swarm optimization (PSO) and Hough transform. The experiments validated that the method proposed can measure the DBH more effectively and accurately.