The essence of continuity principle in educational programs lies not only in the aspect of inheritance, progression in term of proficiency, but also on the teaching content, ensureing that the knowledge that learners get at different levels is consistent and not contradictory. However, recent changes in the 2018 Vietnamese curriculum have highlighted discrepancies in literacy teaching for preschoolers and primary students, hindering the effective transmission of scientific knowledge about Vietnamese letters. To address this issue, this study identifies the areas of change in the Vietnamese language subject at primary level as well as analying the nature of alphabet teaching activities in Vietnamese writing system, and then propose some suggestions for teaching letters to preschool children, ensuring the continuity in teaching content between preschool and primary school levels, thereby facilitating the meeting of the curriculum regulation requirements for teaching Vietnamese to primary students.