As far as current 3D sketching system is concerned, two main problems are obvious. One is few applications on automotive engineering, the other is that pressure-sensitive information is seldom used to create the third direction curve, though both methods of projection and surface intersection are usually used. Based on analysis of current pressure-sensitive technology of digital pen, a system structure of 3D automotive sketching system based on pressure-sensitivity of digital pen was proposed. Then, detailed software surrounding and hardware surrounding on developing the 3D automotive sketching system were proposed. Realization methods of 3D sketching system based on digital pens pressure sensing were important and discussed in detail. There were four steps in the realization methods, which were creating reference plane, extracting pressure-sensitive information, creating and editing 3D curve, creating and editing 3D surface. During creating a 3D curve, the focus was on drawing original curve, dealing with the single stroke and parameterization of stroke, and fitting two curves. Finally, the system was integrated with AutoSketch system and tested, and a prototype for 3D automotive sketching based on pressure-sensitivity of digital pen was completed. The test results showed that the prototype system matched the AutoSketch system well. It was good at high recognition efficiency of operation command and short computation time. However, during the test, it was found that when fitting a single stroke, the beginning and end of the curve could not accurately pass the beginning and end tip of the given data points. The fitting method which is good at clamping might be suggested and adopted.