Abstract: As the founders of Neo-Confucianism, Cheng brothers’ most important theoretic contribution was that they put forth the concept of Heavenly Principle, and established the ontology of Neo-Confucianism. On this basis, Yi-chuan absorbed and remolded the theories of Qi after the Pre-Qin Period, especially during the two Han period. He put them into his thought system and constructed the onto-cosmology of Neo-Confucianism.This new form of cosmology transcended the thinking pattern of the cosmology which only emphasized the movement and transformation of Qi, and represented a response to the challenge from Buddhism.That’s to say,Yi-chuan promoted the cosmology to a new stage.