Abstract: The main performance of hyper-velocity kinetic missile and its solid propellants is described. The mechanism of laser attenuation caused by the plume of solid rocket motor is analyzed. The plume transmittance of two solid-propellant formulations was tested by the aid of a smoke-box when the laser wavebands were 1.06m and 10.6m. The plume transmittance in 1.06m laser was tested with 1.064m laser modulation emitting, receiving and data acqui-sition system. The plume transmittance of 10.6m laser was derived after the optical transmittance of 2m ～13m laser was tested with the blackbody radiation source, spectroradiometer and data acquisition system. The tested data indicates that formulation 2 is better than formulation 1, and the plume transmittance 96%～97% of 10.6m laser is higher than that 92%～93% of 1.06m laser.