Main and spare synchronization method based on data synchronization

The invention discloses a main and spare synchronization method based on data synchronization. The method comprises the following steps that a main system and a spare system are set to be in an interlocking relationship; before each synchronization period starts, the spare system sends data to the main system; the main system judges whether the received spare system data is synchronous or not, if the data is asynchronous, asynchronous marks are output, and asynchronous data is sent to the spare system; if the data is synchronous, synchronous marks are output, and calculation results are output; if the spare system receives the synchronous marks, the synchronous marks are output, main seizing marks are output, and the spare system simultaneously outputs the asynchronous marks; if the spare system receives the asynchronous marks and the synchronous data sent by the main system, the spare system outputs different marks after synchronizing the synchronous data of the main system, and the calculation results are not output. The main and spare synchronization method solves the problems that in the real-time industrial automation control field, the redundancy switching synchronous data quantity is great, so the period time is short, and the data synchronization failure or synchronization error can be caused.