This study examines lexical and syntactic convergence between Dai Lue and Chinese in the multilingual environment of Sipsongpanna, employing an apparent-time approach across three generational cohorts (N = 90, balanced gender). Through mixed-methods analysis (structured questionnaires and semi-structured interviews), significant diachronic variation was observed. Younger speakers exhibited pronounced convergence, adopting Chinese-derived syntactic patterns (e.g., prenominal quantifiers and preverbal adjunct phrases) and borrowing Chinese lexical elements (e.g., an adverb sɛn⁵⁵ ‘first’ ← Chinese 先 xiān, and a superlative marker tsui³⁵ ‘most/best’ ← Chinese 最 zuì). Middle-aged speakers use transitional hybrid structures, while older speakers more consistently maintain native Dai Lue features. The results conform with Labov’s age-grading model in contact linguistics and refine Thomason’s borrowing hierarchy by revealing two factors: First, the prestige of the Chinese language drives convergence among youth. Second, syntactic compatibility with Chinese is mediated not merely by language structure, but by discourse-pragmatic needs, functional load redistribution, and the social indexicality of borrowed structures. This underscores the interplay between sociolinguistic motivations and structural-adaptive constraints in language change. The findings provide critical insights into language contact mechanisms among ethnic minorities of China, with implications for sociolinguistic theory, language revitalization efforts, and bilingual education policy implementation in linguistically diverse communities.