The invention relates to a method for evaluating stability of heavy residuum. The method comprises steps of: mixing a heavy residuum sample with toluene according to a mass ratio of 1:9; adding n-heptane according to a volume ratio of 0.5-3:10 into a mixed solution of heavy residuum sample and toluene after standing; shaking violently for seconds; dumping into a drying clean colorimetric ware rapidly; covering; scanning by a UV spectrophotometer to determine light transmittance of the solution; selecting UV visible light with a wavelength of 740nm as a scan spectrum; processing an obtained light transmittance value by a formula (1), wherein HRS represents stability value, and Ti represents light transmittance of single scan, and T represents average light transmittance of scan, and n represents scan frequency. The larger the values above are, the more stable the colloid structure of the oil product when environment changes. The experimental operation has little difficulty, is beneficial for on-site workers and provides guidance for oil product processing.