The idea "Buddha-nature" first became popular in China in the early fifth century with the translation of the Mahayana Mahapari-nirvana-sutra. Since then, a variety of these have been propounded by Chinese Buddhist thinkers on several aspects of the idea. Ching-ying Hui-yuan (523-597) was a prominent Buddhist thinker of the late sixth century, and an exegete and lecturer of high calibre. In his central work, the Ta-ch'eng I-chang, he devoted an entire chapter to the exposition of the Buddha-nature idea. Basing mainly on the discussion in this chapter, this paper tries to examine Hui-yuan's view on a number of questions which interested the Buddha-nature theorists of his time. These questions include: 1. What is the meaning of the term "Buddha-nature?" 2. What are the distinctive characteristics of "Buddha-nature?" 3. What do the Buddhist scriptures mean when they assert that sentient beings possess Buddha-nature? 4. Dose every sentient being possess Buddha-nature? 5. What function does the Buddha-nature idea serve?