The invention discloses a finite-state machine extended model of a distributed system and a quasi-synchronous method for check points, and solves the problems of poor accuracy and stability in the process of establishing the check points of the distributed system. In the extended model, the distributed system is taken as a set of a plurality of courses; and the finite-state machine extended model is a set consisting of the finite courses: P is equal to {P1, P2, until P0}, wherein Pi represents the courses, i is equal to 1, 2, until n, and n is more than or equal to 2. The quasi-synchronous method is divided into two phases; in the first phase, a coordinating course collects the channel information of each course and judges whether the current state of the distributed system is in a state of global consistency; if the judgment is yes, each course respectively saves respective state and the algorithm is finished; the second phase is a verification phase; and if the current state of the distributed system is not in a state of consistency, a course losing a message is determined and the coordinating course informs a sending course losing the message to resend the lost message till all messages are received or all courses are quitted abnormally due to overtime.