The invention discloses a method for synchronously controlling multiple graph signal generators. The method comprises the following steps of: networking at least two programmable logic devices which both comprise a transmittable/receivable synchronous broadcast packet, appointing one graph signal generator as a synchronization machine and taking the other graph signal generators as synchronized machines; and regularly sending a network synchronous broadcast packet to all the synchronized machines in a local area network through an Ethernet switch, and after the synchronized machines receive the synchronous broadcast packet, realizing operation synchronization of the graph signal generators. The invention furthermore discloses a system for synchronously controlling multiple graph signal generators. According to the method and system, the aim of synchronous operation of synchronous generators is realized and PC synchronization is not needed, so that the production cost is reduced; the synchronization precision is improved and permanent synchronization can be ensured; the graph slicing asynchronization caused by network faults and network delay is solved; and the problem that the synchronous machines cannot be synchronized after faults is solved.