Directional verbs are widely used in modern Chinese. Their constructional changes can be traced back to the Directional Serial Verb Construction in old Chinese. In this paper, we investigate the constructional changes of Chinese lai and qu from the pre-Qin period to the Medieval period from the perspective of constructionalization. This research demonstrates the following findings: Chinese Lai changes into directional verbs. The meaning of directional result constructionalizes the meaning of arrival state, but also persists the meaning of directional time and the causative meaning. Lai undergoes the changes from time deixis to state of affairs in the Medieval period. Chinese qu changes into an intransitive verb and denotes the meaning of getting to somewhere. After a series of constructional changes, Chinese qu produces a new type node and denotes a new meaning. This research proposes that the constructionalization of Chinese lai and qu in SVCs is driven by the principle of economy, and the mechanisms of metaphor and metonymy.