This paper presents the theoretical foundation, practical evidence, and research results concerning the construction of a system of vocabulary exercises for fifth-grade students in line with a competency-based approach. Drawing on the Vietnamese Language Curriculum for primary schools, we have developed a logically structured, diverse and differentiated set of exercises that is pedagogically feasible in vocabulary instruction at primary level. The system comprises five groups: vocabulary expansion; parts of speech, synonyms; polysemy; idioms; and correcting word usage errors. This system contributes to developing linguistic competency in primary students and enhancing the quality of Vietnamese language teaching in Grade 5.