Optical and oxygen sensing property of fluorescent polypyridine complex Ru(bpy)3²⁺ immobillized in the porous glass matrix were investigated. The influence of concentration of complexes in the matrix on intensity of fluorescence and degree of quenching of ruthenium complexes by oxygen were shown. At thickness of matrix 0,5 mm and concentration of complexes on matrix 1*10^-3 Ì sensing element has the highest intensivity of fluorescence and maximum degree of quenching by oxygen. The modified form of Stern - Volmer equation give the best accuracy of approximation for quenching fluorescence. The influence of thickness of the sensing element to intensity of fluorescence and response of sensor is discussed.