Abstract: This paper reported the experiment that used excimer laser(308nm,28ns)to clean the surface of Si substrate. The influnce of laser energy density on laser cleaning was studied. During the test,the energy density irrated on the substrate surface was altered by changing the size of the light beam or adjusting the output energy of the laser.The result obtained was that the cleaning threshold of Si substrate is 0.2J/cm2,while the damage threshold of it is 1.2J/cm2.