Vocabulary plays an important role in learning language as the blocks of a language building and without vocabulary, expressing the intended meaning is impossible (Nation,2006). However, English in Indonesia is still considered as a foreign language, where English is not widely practiced but it is necessary to cope up with globalization. therefore, it is necessary to learn vocabulary as basic need of learning language. According to Lestari (2020) understanding word meaning, and appropriately implementing the words in context is not only unavoidable but also difficult as limited to classroom activities (Lestari,2020). Gu and Johnson (1996) stated that it is important for the learners to have initiative, to additional learning to cultivate their English vocabulary more efficiently. therefore the researcher aims to explore the students’ vocabulary mastery and vocabulary learning strategies. This study used quantitative research method with questionnaire and web based vocabulary test as the instrument. The data for this research are from 81 students of English department from University of Islam Malang. The data was collected through online questionnaire and test with the use of google form. The study used quantitative Pearson correlation and independent sample t test to analyse the data. The result shows a significant correlation between vocabulary learning strategies and vocabulary size that indicated vocabulary size is determined by learning strategies. Moreover, the study also indicated that there is a significant difference between high and low achiever students in vocabulary learning strategies, especially in determination and memorization strategies. But high achiever students are higher in all aspects of vocabulary learning strategies. Keywords: Correlation, English Private and English Achievements