The key point of the “Yuánjué jīng” is to achieve the Buddhahood by cultivating each thought deriving from the Buddha-nature. The meaning of the “Yuánjué” is“complete enlightenment “ (圓覺) , and it is also named “Buddha-nature”, or “reality body”. According to the teachings of the Buddha, “The sentient beings are born with the Buddha-mind which couldn’t be revealed due to the ignorance.” Growing right thought in causal stage is the most important factor to achieve enlightenment, the teaching of the “Yuánjué jīng” is exactly based on complete enlightenment as cause to practice. This study aims to find out the essentials of practice of the “Yuánjué jīng” with the concern of emphasizing this sutra’s value and importance to the practitioners in Mahayana. The research materials of this study are the classic edition of the “Yuánjué jīng” in Chinese, along with the current papers as a supplement. The research methods are based on the principle of adopting Buddha’s teaching to realize the Dharma. The hermeneutics is the major research method, with applying the philology and philosophy as well. This thesis contains six chapters. Chapter one is introduction telling the problem awareness, purpose, research methods, motivation and structure of this paper. Chapter two tells the position of the “Yuánjué jīng” and its feature about thoughts. It also mentions the issue of version authenticity. The relationship between the tathāgatagarbha (如來藏) and the “Yuánjué jīng” is also discussed here. Chapter three, four and five are the focusing statements in this paper. Chapter three deals with the importance of realizing the ignorance－whether it could be swept out or not－effecting the achievement levels of the practitioners. Chapter four explains the way of perceiving: Illusion-leaved and Bodhi-manifested.(離幻顯覺). How to see one's own Buddha-nature (見性) and make cause to achieve complete enlightenment, are discussed in this chapter. Chapter five states the teaching about effecting three kinds of pure contemplation (三種淨觀) to enter the unhindered-gate of the complete enlightenment.（圓覺無礙法門）And, based on it developing 25 kinds of pure and clean meditating ways for becoming enlightened gradually. Chapter six is conclusion. Above three chapters (three, four and five) actually grasp the key point of practice in this sutra, which could be generalized to three steps : Firstly, being a secular, who should give up his ignorance；then, secondly he can see the Buddha-nature. (見性) Finally, by constant practice and realization to gain the Bodi.（修證一貫，得證菩提）This paper discusses the essentials of practice of the “Yuánjué jīng” with the goal of guiding the practitioners to become awakened Buddha.
