Traditional methods of calculating displacement often have certain shortcomings and drawbacks such as high labor intensity and low efficiency. With the help of the 3D laser scanning technique, this paper introduces a displacement computation method based on point cloud slicing technique. The proposed method first segments the point cloud into several point cloud slices along z-axis. The triangle-area-integration method is adopted to calculate the cross-sectional area of each slice. The displacement can be calculated through the accumulation of each slice volume. To compare the results of the proposed methods, the displacement results of corresponding heights computed by commercial software are taken as a reference. Then we calculate the relative expanding uncertainty of the measurement results. The test results indicate that the proposed method can calculate the displacement with high accuracy, thus providing the displacement calculation with a new approach.