Abstract: The phytolith evidence of rice together with AMS 14C dating of charcoal and charred seed from Xishanping site in Gansu shows that the rice has been cultivated about 5 000 years ago in Tianshui, Gansu province. The finding of cultivated rice with accurate dating is known the oldest record, which is also the most northwest border of cultivated rice, in northwest China. The finding extends the record of cultivated rice about 2°of longitude to the west and allows us to estimate the cultivated region of rice 5 000 years ago in Easern Asia. It will help on understanding the affection of rice cultivation and spreading on agriculture and environment.