Most of IELTS students have an excellent knowledge on grammar. Unfortunately, these excellent grammars can not be shown in their Oral English and usually they commit unnecessary and simple mistakes. Although it is not necessary for students to focus on grammar while conversing with other people and vice versa, grammar is an important marking criteria in IELTS oral test. There are a variety of reasons why students commit errors in their grammar during speaking. Therefore, students should be aware of why they are having these faults and start to correct them to be able to have a higher oral band score in the exam. The following are the common reasons why students often commit grammatical error: Translating habit -- The basic translation theory, the differences between English and Chinese language and the common translation skills should be mastered. English and Chinese have different culture background so not all words, phrases or sentences can be directly translated. Some students force themselves to translate everything from Chinese to English. Therefore, most of the things they say seem odd or grammatically wrong because the sentence structure of the two language is different. Usage of He/She---There is no difference in expressing man or woman in Chinese that is why many students always commit this mistake in their speaking. Especially if they are talking in long and complicated sentences they tend to mix he to she. So, some of the students may wonder why they do not have a high score in the test, maybe they have this kind of error during the test without noticing it. Identifying Tenses— Some students may not understand the question of the examiner very well so in their answer, the tenses they use are totally different from the question. Nevertheless, their answer would be totally irrelevant to the topic. Proper tenses are necessary for the listener to understand what you want to express. Misunderstanding will occur if the tense is wrong. Familiarity of Part of speech—Words should be mastered in several ways. Some students have a difficulty to differentiate words in noun, adjective and verb because they tend to concentrate on memorizing only the original word itself .Although it will not affect the thing you want to express but it is considered a serious grammar error. The purpose of learning correct grammar is to help speakers say clearly what they want to express. You can also acknowledge a person’s language ability by how well his/her grammar is. It is sensible to use English grammar as a tool to help you to communicate, understand and master English. You learn grammar only through language phenomena because it comes from it. So you learn those rules and do some exercises to practice them to be able to gain a higher band score in IELTS oral English test.