Abstract: In order to calculate the properties of cladding layer in coaxial laser cladding using energy conservation accurately, the energy attenuation phenomena and rules of laser were researched when laser beam got across through the powder cloud. The powder feed process of a nozzle model was built according to the real nozzle by fluid software and the process that laser beam got across the powder cloud model by finite element software was simulated. The variation trend of powder cloud mass concentration was obtained along with z axis in laser-powder interaction area, and the changing curve of laser attenuation ratio from nozzle exit to substrate in different laser power and powder cloud mass concentration was derived. It shows that attenuation before powder focused is weaker compared to the powder focused region. Quantitative research of laser attenuation ratio is beneficial to the accurate calculation of molten pool temperature field.