This study explores the systematic features and cognitive reasons of English word class errors by Chinese beginner learners of English (CBLE)drawing upon “The Analytical Framework of L1 Transfer during English Word Class Learning” from a grammatical conceptual transfer perspective. It is found that word class errors made by CBLE as an interlanguage were high in frequency and various in error types, namely, “confusions between nouns and adjectives” and so on. The analyses have shown that these errors are systematic, and the cognitive reason for these errors is the grammatical conceptual transfer of Chinese [WORD CLASS]as well as its conceptual properties. These findings have laid a foundation for further studies in terms of Chinese localized conceptual transfer frameworks. Based upon the findings, some implications for English word class teaching and learning are also offered.