Humanistic Buddhism was initially proposed by Master Taixu in early modern times, then refined in theory and verified in practice by a number of eminent monks. It now is a major ideological trend and practical model for Chinese Buddhism in Mainland China, Taiwan, Hong Kong and Macao. Fo Guang Shan in Taiwan, under the leadership of Venerable Master Hsing Yun, has brought the model of Humanistic Buddhism development worldwide. This has become an important channel for Chinese culture to the world. How is it that Humanistic Buddhism has become a major Buddhist ideological trend in Mainland China? How has it become the way for Buddhism to modernize and to survive? Humanistic Buddhism not only responds to the practical needs of this era, but it is rooted in spiritual Buddhist traditions and the Buddha’s original intents. In other words, it is precisely that Humanistic Buddhism has succeeded in “remain adaptable, yet unchanged” and “remain unchanging, yet adapt to circumstances,” as well as closely linking the Buddha’s original intents with realistic social living according to differing aptitudes and needs. In an academic light, Humanistic Buddhism, in this modern era, has actualized the integration of “modernity” and “tradition.” As a result, traditional Buddhism derived a modern feel and vitality. Venerable Master Hsing Yun provided an incisive explanation about Humanistic Buddhism, saying “What the Buddha taught, what is essential to human beings, what purifies, and what is virtuous and beautiful. All teachings that benefit a happy life belong to Humanistic Buddhism.” In fact, this explanation accurately summarizes the “modernity” and “tradition” of Humanistic Buddhism. “What the Buddha taught” expresses the “tradition” of Buddhism, and “what is essential to human beings” comprises the “modernity.” This paper discusses the “modernity” and “tradition” of Humanistic Buddhism through the historical development of Humanistic Buddhism from Master Taixu to Venerable Master Hsing Yun.