Abstact: The biological effect of R.arrhizus was studied by utilizing XeCl excimer laser in condition of radiation power being 2.0 Kv,2.5 Kv and 2.7 Kv,pulse number ranging between 35~135. A peaky lethel curve was found when flood tide was formed at 85 pulse number and low tide was formed at 110 pulse number,which was much distinctively to the lethel curve caused by UV lamp radiation.8 strains were selected through agar flat separation and solid state ferment.their lipase actives were increased by 10 %.Among them,the mutation strain LB-5's lipase activity reach 66.4 IU/g,increasing 55.1% of that than original strains. The connerction of the laser radiation power,pulse number and lethal rate were discussed.