Objective: To look at the fintech regulatory policy and regulatory system in the Greater Bay Area through the lens of the Trilemma of Innovation doctrine in order to identify the applicability and extrapolation of existing legal models in the zone of accelerated economic and innovation development in Guangdong, Hong Kong and Macau.Methods: The article is based on the comparative legal research of the regulation regarding models, existing within the regulatory framework for fintech. For that matter we conduct a generalization, introducing the classification of methods and systems that, in our opinion, can be recognized as the Lego-like systems of instruments.Results: The research evaluates difficulties that may be faced by the participants within GBA on the way of legal harmonization regarding fintech. Special attention is paid to Hong Kong SAR, being one of the bestknown examples of successful fintech regulation, and to comparing fintech regulation in Mainland China and in SAR (Macau, in particular). The author states that the last amendments to the financial law of Macau SAR also add an element of uncertainty, even though they aim to develop the situation within the framework. The author compares a technocratic approach, according to which fintech regulation is completely national (created only for the domestic market and reflects its structure) and traditional approach to regulation, a part of which is the Trilemma of Innovation. The latter implies the possibility of over-national (international) standardization, including in the form of soft law, which may eliminate the difference in understanding the fintech characteristics, its concepts and scope. Besides, the author analyses the correlation between the concepts of financial regulatory system and financial system of fintech regulation, extrapolation of the existing regulatory framework to the developing market of innovative technological solutions and their various models. The author highlights the regulatory response method, changing during the fintech market evolution, and applied, as a rule, together with other approaches.Scientific novelty: the article presents a comprehensive review of the different systems of fintech legal regulation in the Guangdong – Hong Kong – Macau Greater Bay Area, whose unique experience demonstrates various trajectories of the fintech market development in southern China within the “One Country – Two Systems” concept.Practical significance: the main conclusions and proposals resulting from the study are of significant interest for further research, regulatory policy and fintech regulatory system, as Mainland China and the special administrative regions of the Greater Bay Area use different approaches and methods of legal response that have no analogues in the modern world.