The defeat of Sasanian in Nahavand led Yazgird III (632_651A.D), the last sovereign of this dynasty, to take refuge in the eastern territories of Iran. He made alliance with Iranian aristocrats to restore the control of his lost lands, however he did not succeed. The son of Yazgird, piruz, and the Iranian aristocrats took refuge in the court of tang, which was located in China after the death of Yazgird. They continuously endeavored to release Persia from the control of Arabs by alliance with Chinese, Sogadians and thokhtariyans, however their attempts failed. This article tries to present a clear narrative from last Sasanians in Thakharestan, China and Japan by criticizing the available information in early Islamic and Pahlavid texts, Chinese and Japanese historical reports, archaeological studies in China and recent researches.