There were two different chronometry systems in ancient China. One was the 12-earth-chronometry, which divided one day into twelve equal parts, called Shichen in Chinese. The other was the 100 units of chronometry, which divided one day into 100 equal parts. The unit was Ke in Chinese term, originally meant the notch of the arrow in a clepsydra. The Chinese people began to combine these two systems together from Sui and Tang Dynasty (7th century). However, because one hundred and twelve were not commensurable with integral number, so they used a very complicated way to combine the two systems. In the late Ming Dynasty (17th century), when Jesuits came to China and took part in the Chongzhen Calendar Reform, they began to use the 96 units in calculation. The New Western Calendar, which adopted the 96 units of chronometry, was promulgated by government in the Qing dynasty. Adam Schall said that the 96 units were more convenient for calculation. However, a man named Yang Guangxian accused Adam Schall and the New Western Calendar in 1664. The 96 units of chronometry were also targeted, Yang Guangxian supposed that the 96 units made one day shorter than the 100 units. At that time, the political circumstance was unfavorable to Adam Schall, the 96 units were supposed to be a mistake of the Western Calendar, so the 100 units replaced the 96 units again. Ferdinand Verbiest defeated Yang Guangxian in the test of moon’s orbit, etc. in 1669, which demonstrated that the Western calendar was better than Chinese calendar. Verbist refuted Yuangxian’s charge that the 4 units were the superabundance of the 100 units of chronometry, not the less of 96 units. Moreover, The 96 units did not make one day shorter. Then the Western Calendar and the 96 units were finally established in China. After that the hour, minute, second system was also established in China. However, the later Chinese scholars didn’t acknowledge that the 96 units of chronometry came from western in the thought of “the theory of western learning being of Chinese origin”. To sum up, the Jesuits took accommodation policy to adapt Chinese tradition in the field of chronometry. And the 96 units of chronometry had the same fate with the Western Calendar. Moreover, the debate between 100 units of chronometry and 96 units of chronometry came from the different metrological system adopted by Chinese calendar and Western Calendar.