This longitudinal study examines the directionality and transfer mechanism of cross-linguistic transfer of phonological awareness between L1 and L2 in predicting early writing in Chinese children learning English as L2. Results show that there is a bidirectional cross-linguistic transfer of phonological awareness and early writing between Cantonese and English with large linguistic distances. Although there is no direct impact of source language phonological awareness to target language writing due to the large language distance between Cantonese and English, the source language phonological awareness can affect the target language phonological awareness via target language-related skills.To enhance the development of  Cantonese character writing and English spelling, practitioners are suggested to closely monitor students’ learning performance in L1 and L2 phonological awareness as well as design learning activities.