Many experimental observations show that the fluorescence-disappearance phe-nomenon happens at somatic body,biobody,and other materials. This phenomenon is due to the nonlinear interaction between their surface and the laser. Experimental study on the leaflet of plant shows that fluorescence-disappearance phenomenon is a multiphoton process,and is accompanied with second harmonic generation.During fluorescence-disappearance process,the fluorescence energy is transfered into second harmonic signal partially，after roughly counted，the transfer coefficient is about 2.2%.