A physical model of small scale space debris irradiated by laser was established. The relation between the speed increment of small scale debris and the laser power density was investigated by numerical simulation,and the laser effective acting time was obtained under different power densities. Further,the waveforms and arriving position of shock wave propagation with different laser pulse widths were analyzed. Finally,the change rules of impulse coupling coefficient with different laser pulse widths and power densities were analyzed. The results indicate that the velocity increments increase with the increase of power density,and the shock wave has obvious broadening effect. Especially,the short wavelength can obtain the larger impulse coupling coefficient when the power density and pulse width are definite.