This study examines the seven and ten types of tathatā presented in the Saṃdhinirmocana-sūtra and the Cheng weishi lun, and compares their interpretations in Woncheuk’s Commentary on the Saṃdhinirmocana-sūtra and Kuiji’s Cheng weishi lun shuji. Its purpose is to clarify the relationship between these two typologies and to demonstrate that the Yogācāra doctrine of tathatā is fundamentally structured as a theory of Buddhist practice. The study shows that the seven types of tathatā in the Saṃdhinirmocana-sūtra systematize the content of yathāvadbhāvikatā (如所有性) as the object of meditative contemplation, whereas the ten types of tathatā in the Cheng weishi lun explain the progressive realization of tathatā through the stages of practice. Thus, the former represents the perspective of the object of contemplation, while the latter represents the perspective of realization. A comparison of Woncheuk and Kuiji reveals that both accept the non-differentiated nature of tathatā and regard the sevenfold and tenfold classifications as provisional. However, Woncheuk adopts a harmonizing approach that integrates diverse textual traditions, whereas Kuiji systematically interprets the typologies according to the principles of yuequan bianti (約詮辨體) and cong nengquan shuo (從能詮說). This study concludes that the transition from the sevenfold to the tenfold typology does not indicate a transformation of tathatā itself, but reflects a shift in Yogācāra scholasticism from explaining the true nature of reality to systematizing the stages of Buddhist practice. The seven and ten types of tathatā respectively correspond to the object of contemplation and the realization of awakening, together constituting a coherent practical framework of Yogācāra.