Learning Chinese as a second language is challenging for non-Chinese speaking population in Hong Kong. In order to facilitate the Chinese learning of this group of people, understanding their trajectory of Chinese language development is crucial. The present longitudinal study follows 88 non-Chinese speaking preschoolers in 4 time points, from their K1 to K3, in order to have a grasp of their Chinese language development in three key aspects, namely listening, speaking and reading. Results showed that non-Chinese speaking preschoolers progressed their Chinese language proficiency over time in the three domains, whereas their listening abilities have the best advancement. Though their speaking abilities were the worst at the beginning, they had significant improvement by the end of their K3. The qualitative data provides descriptors of the Chinese language proficiency of non-Chinese speaking preschoolers in different grades. The study's findings serve as a valuable reference for schools regarding school-based curriculum development, learning and teaching materials, approaches and assessments. Copyright © 2021 Academy Publication Co., Ltd.