Legal translation holds a pivotal position in the development of the international rule of law, functioning as a channel for the cross-legal system and cross-language communication of legal knowledge. From the perspective of Transknowletology, legal translation encompasses not only the processing, reconstruction, and communication of legal language and cultural elements, but also manifests the transformation and integration of knowledge localization. Language serves as the medium through which law is articulated and preserved. Certain legal terminology has persisted since ancient times, which is a phenomenon ubiquitous across legal languages globally. The use of Archaic Words within legal language is particularly prevalent, underscoring the formality and authority of the law, which makes them harder to translate. This paper delves into the translation level of knowledge and the knowledge level of translations embedded in Archaic Words from the perspective of Transknowletology. The former, the translation level of knowledge, pertains to the language knowledge level, which encompasses precision, formality, historicity, and logical coherence in Archaic Words. The latter, the knowledge of translation, aims to the skills knowledge level, including translation methods, such as literal translation, free translation, and addition and omission. The goal is to forge an interface that fosters a positive interaction between the translation level of knowledge and the knowledge level of translation, thereby furnishing comprehensive and multilevel knowledge support for legal English translation endeavors.