Some important documents, such as the Tangut legal texts “Revised and Newly Approved Code of the Heavenly Prosperity Reign (1149–1168)” (Tiansheng lüling) and “New Laws of the Pig Year” (Hainian xinfa), are not fully clarified. One reason is that some Tangut words cannot be understood correctly. The main key to finding exact meanings of Tangut words are translations of Chinese classics. In this paper it is shown how using the Tangut translation of a Chinese leishu, “Forest of Categories” (Lei lin), and finding correct interpretations of nine words results in reasonable translations of legal provisions.