Abstract: Downstep in pitch contour of Mandarin Chinese is examined using subtly designed sentences, by controlling tone combinations. The results show both automatic and non-automatic downstep exist in Putonghua. In non-automatic downstep, the low tone will compress downwards the pitch range of following syllables, and the main influence of downstep is on topline. Low tone will not only lower the topline behind it, but also raise the high tone before it, both effect can be compatible with each other in Chinese. In automatic downstep, the topline of intonational phrase pitch contour is presented as a linear downtrend. But there are different results among speakers because of the effect of stress. In addition to these, by comparing with the downstep in other tone or non-tone languages, in Chinese, the ratio of downstep is not constant, and the domain of downstep is not limited within the adjacent tones .