The invention relates to the technical field of an electric power system, and particularly relates to a large-scale distributed power supply grid-connected island detection method. The large-scale distributed power supply grid-connected island detection method is characterized in that a chaotic characteristic and a Lyapunov index are introduced into distributed power supply grid-connected island detection, and the Lyapunov index of a distributed power supply is recorded in the whole course in the testing process so as to perform accurate and reliable island detection on the distributed power supply. The method provided by the invention reduces a dead zone of traditional island detection, improves the accuracy and the reliability of passive island detection, applies parameter variations of the chaotic characteristics in the large-scale distributed power supply island conversion process to large-scale distributed power supply passive island detection, and can effectively avoid a phenomenon that a traditional passive island detection method causes island detection misoperation because of variations in operation condition.