This article mainly examines Master Taixu's communication of exoteric and esoteric Buddhism with a focus on Japanese Mantrayana's return back to China at the beginning of the 20th century, which is an important historical event with multiple meanings. In the end of 19th century, political changes and social transformations in China provided a critical opportunity for Chinese Buddhism to be revived. At that time, Chinese Buddhism was declining and the demand for reform was growing. Japanese Mantrayana back to China reflected the imbalanced sino-japanese relations in politics, religion and culture. The exchange of exoteric and esoteric Buddhism was actually a one-way input. In 1918, when Wang Hong-Yuan translated Gonda Raifu's the Essential Note on the Singon School, Master Taixu pursued the second stage of Buddhist reform. With the very idea to spread eight schools of Chinese Buddhism all together, Master Taixu regarded the revival of Mantrayana as an important part of the reform. Under his encouragement and the influence of his famous Buddhist magazine Haichao Yin (Sound of the Tide), this period saw Mantrayana study became a trend for Chinese monks travelling to Japan. Those from Tain-Tai and Hua-yan schools went to Japan one after another to lean Mantrayana practice. The quick development of Japanese Mantrayana in China persuaded, however, the sponsors of Master Taixu to change their faith from exoteric to esoteric Buddhism. As a result, the Wu-Chang Buddhist College founded by Master Taixu was nearly closing down due to lack of support. Some controversy erupted afterwards between exoteric and esoteric Buddhism over disciplines and doctrines, but Master Taixu still ideally and realistically insisted on his aspiration to revive Mantrayana. He never changed his mind even when the Wu-Chang Buddhist College was in times of crisis.