Vocabulary is one of the important language elements to be learned by students in learning a foreign language. Having a sufficient vocabulary as well as mastering the use of vocabulary is important for students to be able to use the language well. Vocabulary is not taught specifically at school but it is commonly taught integratedly with other skills such as reading comprehension in teaching and learning process. Therefore, this study intends to find out the students’ mastery of vocabulary of descriptive text for the seventh grade of SMP Negeri 25 Banjarmasin by employing quantitative method. There were 32 students as the samples in this research by using cluster random sampling technique. The instrument was a test by using Google Form of filling in the blanks which consisted of 50 items.

The result of this research showed that the students’ mastery of vocabulary of descriptive texts for the seventh grade of SMP Negeri 25 Banjarmasin was poor. It was found that the mean score of students’ mastery of vocabulary was 61,31 in test 1 and 61,19 in test 2. They were in the poor category because their mean scores were below KKM of SMP Negeri 25 Banjarmasin. Most students felt difficulty with the word meaning, word choice, word position and word function of parts of speech in the sentence.

The researcher proposed some suggestions: (1) the students of SMP Negeri 25 Banjarmasin need to learn more about vocabulary, especially on nouns, verbs, adjectives and adverbs by looking at the word forms, their function and their position in sentences and (2) it is also recommended to the students to read more to increase their vocabulary mastery and read many different texts from a variety of sources to broaden their knowledge.