The Buddhist Tzu Chi Foundation has been established by Dharma Master Cheng Yen for over half a century. It is one of the largest NGOs among the Chinese populations. Most studies on Tzu Chi (TC) are concerned with its charity work, organization development, and its influence on TC volunteers. There is little research on the role of the TC Jing Si Sanghaor its "Spirit of Great Love". Taking the Sangha as the object of study, this thesis reviews the formation of the concept of Great Love as promoted by Master Cheng Yen. An empirical approach is used to investigate the influence of the Great Love spirit upon the Sangha and the TC organization at large. The author takes an "insider's" standpoint to study the Sangha's praxis of Great Love. Three sources of data are collected for the study: documents, field-work interviews, and participant observation. Documentation comprises of the publications of Master Cheng Yen, audio-visual recordings of her public addresses, and archival materials of TC history and the Sangha. The author has interviewed over 40 Bhikshunis (Buddhist nuns); the narratives of twentyof them about their "cultivation experience" are quoted. The author analyzes the scripts and describes how the Sangha realize the spirit of Great Love. The author identifies four characteristics of TC Jing SiSangha's"Style of Cultivation" which differs from that of traditional Buddhist sanghas. They are "self reliance", "self restraint, frugality, diligence, resilience", "abide to the Buddha's heart and to the Master's goal", and "the Sangha's unconditional support of TC". The Master defined the concept of Great Love in 1983. The author summarizes the meanings of Great Love as follows: its three "static contents" are personal vow, dharma wisdom, and compassion;and its four "dynamic aspects" are "recruiting resources for altruism", "transforming desires and worries", "gathering love from multiple religions", and "confronting social ills". The Master has never stopped injecting Buddhist spirit in her formulation of the idea of Great Love. She urges the Sangha and TC volunteers alike to "practise Tzu Chi [volunteering]" as a way of self cultivation. Finally, this study clarifies some misunderstandings of the TC history. As to the management of the Sangha and that of the Foundation, the author remarks that the two had separated their finances from the early days. The principle of self relience has been followed by the Sangha to this day. Though not receiving any funding from the Foundation, the Sangha has maintaineda very close relationship with it especially in the spiritual and religious aspects.