重構儒家的性論，是張載對抗佛老的重要路徑。其性論蘊含著一定的邏輯層次：首先，把儒家底色的性提昇為天道，從根源處與佛老分別開來，並將性與從道家吸取的太虛與氣相融貫，構成三層天道觀；其次，把天道之性下貫至形下層面，進而區分人性與物性、天地之性與氣質之性；再次，對應於天地之性與氣質之性，提出從正面徹見天地之性和從反面變化氣質之性兩種盡性工夫；最後，盡性工夫的完成，則是見性境界或成性境界。成性有「一節而成性」和「於大以成性」之分，且從人格、價值和狀態等多維度呈現。這種從天道出發，最終又回歸與天道為一的性論，是張載天人關係論在其性與天道問題上的反映。

Reconstructing the Confucian theory of Xing is an important way for Zhang Zai to fight against Buddhism and Taoism. There are some logical levels in his theory of Xing. Firstly, the nature of Confucianism is promoted to Tiandao, and then it is integrated with the Taixu and Qi absorbed from Taoism to form a three-level Tiandao. Secondly, Xing is down to the metaphysical level, and then Renxing and Wuxing, the Xing of Tiandi and Qizhi are distinguished. Correspondingly, the Xing of Tiandi can be seen from the positive side and the Xing of Qizhi can be changed from the negative side. the completion of the utmost effort is the state of Chengxing or Jianxing. There are two kinds of Chengxing: Yuyijiechengxing and Yudachengxing, and it can be embodied from the perspectives of personality, value and state. In the end, the relationship between Xing and Tiandao is reflected in the theory of heaven and human.