The cave-temple complex at Bāmiyān lies in the Hindukush Mountains, about 230 km west of Kabul, the capital city of Afghanistan. Based on the reorganization of relevant literatures, archaeological discoveries and carbon-14 dating results and the mutual verification among them, the article considers that the age of building the cave-temple complex at Bāmiyān, especially the two giant standing Buddha statues, shall be around 600 CE, the time when they were built by the preceding king of the country as recorded by Xuan Zang. And the completion time of most niches and caves could be dated back to the period from the 7th to 8th centuries. Through analysing the shape and structure of niches and caves at Bāmiyān, the layout and combination, the rich contents of statues and frescoes, as well as historical documents, it also suggests that both Mahāyāna and Hīnayāna all prevailed during the 7th century in Bāmiyān. As Chinese Buddhist monk Yijing thought, these two schools remained rooted in the foundational teachings of the Buddha while different.