In order to improve the accuracy of the mechanical key component model constructed by 3D laser scanning and reduce the economic loss to the marine port, the factors affecting the accuracy of 3D laser scanning were studied. By studying the error of the instrument, errors related to the target object, errors caused by external environmental conditions, errors caused by human operations, and errors caused by different measurement methods were discussed. In view of the errors caused by different measurement methods and different measurement methods for different parts, the scanning experiment was carried out and the obtained data was analyzed. A method of improving the scanning accuracy was proposed, which made the three-dimensional scanning more accurate. This method was applied to the design of key part structures for marine port machinery. The results show that the research in this paper can help designers accurately and completely obtain 3D point cloud data of mechanical key parts, improve scanning accuracy and reconstruct 3D model. Therefore, according to the application prospect of 3D scanning technology and the status quo in China, it is of great practical significance to study the accuracy of 3D laser scanning technology.