Abstract: Mandarin Chinese is topic-prominent, and it also features subjectivity. However, previous researches have up to now never correlated these two features of Chinese, nor have they systematically examined the subjectivity of the topic-comment construction together with its motivation. The paper expostulates that the bleaching of the spatiality of the topic and the temporality of the comment paves the way for the construction’s subjectivity. In this paper spatiality and temporality are taken as a continuum, and the weaker they are, the more subjective the sentences are. Spatiality and temporality are correlated with subjectivity from two dimensions: spatiality and temporality bleaching makes the way for virtuality of thinking and linguistic operation on the one hand, and weak or vague grounding on the other, thus resulting in subjectivity.