This paper explores the philosophical significance of the concepts of tiandi 天地 (heaven and earth) and qi 氣 (psycho-physical energy) in their correlations with classical Confucianism. Choi Shihyung adopted the meaning of tiandi in the Yizhuan 易傳 and held that tiandi generates all things and grows them as like parents with virtues in human society. Nevertheless, his understanding of the correlation between heaven and man is distinguished from that of the Yizhuan in the following aspects. First, the authors of the Yizhuan focused on the correlations between tiandi's movement and human creation of culture or moral teaching by the sages. In contrast, Choi shifted the focus of the heaven-human relationship to human life-related issues and attempted to show that the pro-life movement of tiandi aims at supporting the survival and flourishing of human beings by providing sustainable food. Second, the Yizhuan contains the teaching of respect toward tiandi, but it does not treat jing 敬 (respect) as the most overriding and essential virtue. Choi, however, considered the jingwei 敬畏 (respect with awe) toward tiandi as the core virtue humans should cultivate, which shows his stronger ecological ethics than that of the Yizhuan. Moreover, when Choi expounded the movement of tiandi by utilizing the concepts of li 理 (Principle) and qi 氣 (psycho-physical energy), he put more emphasis on qi than li. This is similar to qibenlun 氣本論 in some of the Neo-Confucianism traditions. But his thought is distinguished from the Neo-Confucian qibenlun in that he stressed the positive aspects of qi by liberating qi from the restraint by li. Besides, his qibenlun is distinct in the sense that he claimed that qi is the energy of the anthropomorphic deity, haneulnim 하늘님. In this respect, it can be said that his qibenlun is more developed and articulated than that of the Neo-Confucian qibenlun.