Laser direct manufacturing and re-fabricating have been used in many important fields in recent years. However, simulation and measurement of velocity fields in carrying gas and powder particles are still a challenge. In this paper finite difference method has been selected to simulate the velocity fields of powder/gas fluid. A novel DPIV system has been developed to measure the velocity fields. The DPIV system mainly consists of Nd+:YAG laser and CCD camera. Comparing the result of DPIV measuring with computer simulating, a good agreement can be obtained. After further developing, DPIV will become a useful device for laser manufacturing.