Phonological fossilization, particularly in terms of pronunciation, presents a significant obstacle for second language learners in further advancing their language proficiency. Therefore, this study, grounded in the theory of interlanguage fossilization, aimed to investigate Mandarin native speakers learning Indonesian as a second language. By designing tests for the target group, collecting data on phonological fossilization, and analyzing the fossilized phonemes produced during the process of learning Indonesian, this research identified the underlying causes of phonological fossilization from both phonetic production and knowledge perspectives. Subsequently, corresponding strategies were proposed to overcome phonological fossilization, with the ultimate objective of improving the language skills of second language learners. This study contributes to the understanding of phonological fossilization in second language acquisition and offers practical insights for language instruction.