No final conclusion has yet been reached in academia on the time of commencing Manchu seal characters. After a thorough and systematic examination of the earliest official seals made in Later Jin Dynasty which are extant, this paper finds that neither the “Imperial Seal of Jin Khan” nor the “Destiny Imperial Seal of Jin Khan” were made in Manchu seal characters but rather regular script of old Manchu characters in Uighur and Mongolian style. Based on the fact that the official seals of six Ministries made in pure Manchu seal characters were started using in 1632 (the eighth day of August in Tiancong Year Six according to lunar calendar),the researcher argues that the time Manchu seal characters were commenced is some day between the half year period from the seventeenth day of January (or the first day of March, the new Manchu character was approved) and the eighth day of August (the official seals of six Ministries started in use) in 1632 (Tiancong Year Six). In the light of the styles and characteristics, this paper divides the development of Manchu seal characters into three phases: the commencing stage before Manchu passed Shanhaiguan into central China in 1644; the quiet stage after Manchu passed Shanhaiguan; and the maturation stage after the accomplishment of “Eulogy of Mukden by Emperor Qianlong” in 32 Fonts of Manchu seal characters in 1748 (Qianlong Year Thirteen).