This paper describes a perceptual study on approximated Cantonese tone contours. It is found that Cantonese tone contours and tone transitions can be approximated by a limited number of linear movements, without creating any noticeable perceptual difference. The slopes of these linear movements are analyzed. They are found to be related with two thresholds of pitch movement perception. The results of perceptual tests with polysyllabic words over large segmental variation confirm the feasibility of approximating F0 contours of Cantonese speech. Index Terms— Tone perception, Cantonese tones, perceptual equivalence, speech naturalness