The results of laboratory studies of optical properties of bitumen of Mordovo-Karmalskoye field, data on thermal conductivity of reservoirs, results of statistical processing of laboratory and actual data are analyzed. The influence of conditions of thermal influence and thermal conductivity of reservoirs on optical properties of produced bitumen has been investigated. Correlation interrelations of bitumen optical properties with temperature conditions of their development, thermophysical and heat capacity properties of reservoirs and bitumen typing by optical properties are revealed. Recommendations on elimination of thermal effect are given.