This paper aims to use the application of Yin-Yang theory in bone remodeling to address the nature of Yin-Yang theory in TCM. Here we propose that osteoblasts (bone-forming cells) and bone formation should be considered Yin, while osteoclasts (bone-resorbing cells) and bone resorption should be regarded as Yang. Moreover, we argue that the Yin-Yang relationship exists between osteoblasts and osteoclasts, and we conclude that the relationship between osteoblasts and osteoclasts as established in contemporary biology reflects the classic Yin-Yang in bone homeostasis. Therefore, the new Yin-Yang concept of osteoblasts and osteoclasts in bone homeostasis may strengthen the basic theory of TCM as well as guide clinical practice.