Minority students' English learning is a special and an indispensable component of English education system in China. This article studies students' linguistic knowledge that live in Northwestern China--Gan Nan Autonomy State of Gan Su Province with majority population of Tibetan, mixed with Chinese and some Muslim. An analogous analysis is conducted between L2 students (Chinese students who learn English as a second Language) and L3 students (Tibetan Students whose first language is Tibetan, second language is Chinese, and third Language is English) in English Linguistic Knowledge. The linguistic knowledge is constituted of vocabulary, grammar and reading skill. (Raykov, T, & Marcoulides, G.A, 2006) The paper concludes the remarkable difference exists between the Tibetan Students and Chinese students in Linguistic Knowledge, especially on vocabulary and grammar. The difference on reading skill is apparent, but not significant. The reasons that caused these distinctive or non-dramatic differences are explored and further discussed respectively.