Abstract: Propagation and properties of vapor plume plasmas generated by Nd : Glass laser pulses interacting with Ly12 aluminum targets were investigated with high speed photograph technigue, and then the sheilding effects of absorption were studied. Experiments show that the optical thickness is up to 1.2 for power densities between 0.7 × 10⁷W/cm² and 1.6×10⁷W/cm². The absorption of vapor plume plasmas is proportional to the incident laser intensity, and the absorption curve vs time of peak pulse was abtained experimentally. The absorptivity is greater at 3mm apart from the target surface than at 9mm.