The Mahayana Buddhist idea of Two Obstruction is Defiled Obstruction and Obstruction of Knowledge. The idea provides a clear cut explanation on the difference between Mahayana and Hinayana’s interpretations on ignorance. However, the exact meaning of Obstruction of Knowledge is so far unclear in the modern scholarship. The purpose of this article is a studying on parahita-caryā-akāmana-āvaraṇa, the 9th level of Obstruction of Knowledge, which among all levels of jñeyāvaraṇa, has the most profound Mahayana implication. The studying is mainly based on the Vol.10 of Hsuanchuang’s Cheung Wei Shih Lun, along with other Yogācāra sāstra and sutra. What the 9th level of Obstruction of Knowledge means is the advanced practitioner of Mahayana Buddhism unable applying language in a precise, creative and perfect way, to develop systematical knowledge. Thus, he is not yet able to fully achieve the four various levels of intellectual capability in verbalization, namely, catvāriṃpratisaṃvid. Furthermore, the subject matter will also indirectly connected to other important Mahayana ideas related, such as five branch of science (pañca vidyā), and omniscience (sarvajñā).