1. A file synchronization method, wherein the file synchronization method is applied in a hybrid system which has a first system and a second system, the method comprising steps of: monitoring, by the first system, a first cache of the first system, in which first data corresponding to a first file stored in a non-volatile storage of the first system opened by a first file processing program of the first system is saved; sending, to the second system, operating content performed by the first file processing program on the first file via a data information channel between the first system and the second system, when the first data in the first cache is changed; and performing a synchronization processing on a second file by a second file processing program in the second system according to the operating content, wherein the second file is a file corresponding to the first file in the second system, and is stored in a non-volatile storage of the second system.