In the present paper, polylactic acid (PLA), poly (butylenes succinate) (PBS) and polycarbonate (PC) were selected as test coating materials, and the variations in their IR spectra under conditions of outdoor illumination and pot incubation were studied, aimed to approach the degradability of these coating materials under sunlight and in soil. The IR spectra showed that after 4 months under outdoor illumination and pot incubation with brown soil and black soil, all the test coating materials had definite variations in their structural configuration, being more obvious under pot incubation than under outdoor illumination, which suggested that the test materials were degradable, and the degradability was greater in soil than under sunlight. PC had the greatest degradability, followed by PLA, and PBS. The degradability of PLA and PC was greater in black soil than in brown soil, while that of PBS was reverse.