A simple and useful new method of measuring the absolute fluorescence quantum efficiencies of laser dyes by thermal lens effection is described in this paper. Using this method, we measure the absolute fluorescence efficiencies of oxazine 1 perchlorate (Ti njin Dye Institute, China) which is dissolved in several different solvents and different conoentra-tions, and discuss the unusual phenomenon, i.e. when the dye is dissolved in the 1, 2-dichloroethane or trichlotome-thane, it has much greater quantum efficiency than in the ethanol absolute, water etc. Wethink, retraining the vibrations between atoms of chromophore will be a effective way to imporve the absolute fluoresoence quantum efficiencies of 1aser dyes.