The helical intake port geometry directly controls swirl ratio, volumetric efficiency and combustion characteristics as well as emissions reduction of diesel engine. A new digital design method of helical intake port was studied. In this method, cylinder head structure was considered as a constraint condition, and the swirl ratio was considered as the design target; then the flow coefficient was optimized. The effect of the geometry structure and port sensitive areas of diesel engine helical intake port on the intake port flow characteristics was analyzed, and several key structural parameters of helical intake port were defined. As a result, a parameterized mathematical model of helical intake port was established. Based on parameterized mathematical model of helical intake port and several key structural parameters of helical intake port, a digital modeling software about diesel engine helical intake port was developed. For the design requirements of helical intake port of selfdeveloped horizontal twocylinder diesel engine, a digital 3D model of helical intake port was established by using the helical intake port digital modeling software, and model smoothness and flow characteristics of this 3D model were analyzed. The results show that helical intake port digital design method has a certain feasibility and versatility. Just providing with the design requirements of the cylinder head structure and flow characteristics (swirl ratio and flow coefficient), a helical intake port that meets the requirements can be designed through using the digital design method and modeling software.