This paper proposes a multimedia English learning (MEL) system, based on Hidden Markov Models (HMMs) and mastery theory strategy, for teaching students with the aim of enhancing their English phonetic awareness and pronunciation. It can analyze phonetic structures, identify and capture pronunciation errors to provide students with targeted advice in pronunciation, intonation, rhythm and volume. In addition, the paper also applies the mastery learning to effectively help students practice pronunciation of English words and sentences. Finally, this paper adopts a quasi-experimental design and lasting for 12 weeks and 120 third-graders, aged 9-10 years, from an elementary school in Yunlin County in Taiwan. These students were recruited and randomly assigned as the experimental group and the control group, respectively. The former used the MEL system, while the latter received the conventional English teaching. Research data were collected through the Phonemic Awareness Test and the English Achievement Test. The results showed that the experimental group with low phonemic awareness performed significantly better than the control group in the English Achievement Test. (Contains 11 figures and 6 tables.)