In this paper, a new generation method of external synchronization for camera exposure control is proposed, which can meet the requirement of real-time error compensation. This system consists of a series of hardware and software. General GPS receiver, receiving and collating signal module and external synchronization signal level matching module belong to the category of hardware. The software includes various modules of external synchronization signal in programming logic circuit, there are generation and adjustment module for frequency, error analysis and adjustment module, the signal generating module and the module of matching with camera logic. The GPS receiver receives satellite signals and outputs B code in real-time, receiving and collating signal module converts the B code into a level signal matching capability of programming logic circuit, synchronous signal of target camera is generated through a series of processing module in programming logic circuit, and then it will be converted into suited signal level to control camera exposure in external synchronization signal level matching module. In practice, the method can realize the precise adjustment of the camera exposure time without adding additional devices. The method improves the accuracy of the time series of the continuous image sequence from dozens of microsecond level to single microsecond level.