By using the reservoir techniques of microscopy fluorescence, according to fluorescence in the distribution of pore throats and intensity of fluorescence, reservoir microscopic fluorescence can clearly reflect the pore and throat as well as connectivity conditions in the pore structure, and then reveal the reservoir quality and gas bearing. Taking the sandstone reservoir of Xujiahe formation of upper Triassic in Shunan area of Sichuan basin as an example, the fluorescence characteristics and gas bearing property of pore type reservoir and fracture pore type reservoir are expounded respectively, and the pore lower limit of the two types of reservoirs is determined by combining the measured physical property data. The results show that the microscopy fluorescence distribution and intensity in the pore throat can be divided into three types of fluorescence levels. The reservoir microscopy fluorescence method can directly and reliably reflect the reservoir oil and gas potential. The lower limit of physical property determined by this method is consistent with the intersection method of porosity and permeability, the minimum pore throat radius method and the oil testing method, which proves that the method of determining the lower limit of gas bearing property and physical property by microscopy fluorescence is effective under the condition of incomplete data.