Recently, HSDI (High Speed Direct Injection) diesel engine has been spotlighted as a next generation engine because it has a good potential for high thermal efficiency and fuel economy. This study was carried out to investigate the in-cylinder flow characteristics generated in a 4-valve small diesel cylinder head with a tangential and helical intake port. The flow characteristics such as coefficient of flow rate(Cf), swirl ratio (Rs), and mass flow rate (ms) were measured in the steady flow test rig using the impulse swirl meter and the analysis of in-cylinder flow field was conducted by experiment using the PIV and calculation using the commercial CFD code. As the results from steady flow test indicate, the mass flow rate of the cylinder head with a short distance between the two intake ports is increased over 13% than that of the other head. However, the non-dimensional swirl ratio is decreased approximately 15%. From in-cylinder flow characteristics obtained by PIV and CFD calculation, we found that the swirl center was eccentric from the cylinder center and the velocity distribution became uniform near the TDC. In addition, the results of the calculation are good agreement with the experimental results.