This study aims at giving light on the meaning of ‘Sincerity’(誠: Cheng) and ‘reverent seriousness’(敬: jing) in its system of self-cultivation accomplished by Jeung-San. ‘Sincerity’(誠:Cheng) and ‘reverent seriousness’(敬: jing) should be required necessarily for the mental state of ‘In-jon’(人尊) as an ideal symbol that the thoughts in Jeung-San eventually would achieve. these two concepts mean certain methods for self-cultivation as a right attitude towards it. Regarding these concepts as important ones for the above reason, this paper focuses on what the concrete result could be as the ultimate goal for cultivation. In order to clear up the meaning of ‘Sincerity’(誠: Cheng) and ‘Reverent seriousness’(敬:jing) in self-cultivation by Jeung-San, this paper not only deals seriously on details with the understanding of Confucious meaning of (誠: Cheng) and (敬: jing), but also make an effort on grasping the various aspects in meaning of (誠: Cheng) and (敬: jing) on several religious thoughts and other pre-existing philosophical ones. In this process of consideration, it studies on how the meaning of these two concepts had been sublimated by means of a comparative viewpoints with presenting resources. Therefore, this studies purposes the clear understanding for its peculiar feature that the methods of ‘Sincerity’(誠:Cheng) and ‘Reverent seriousness’(敬: jing) as self-cultivation would intend to put great emphasis upon the practical inclination with cultivating self for oneself.