The invention relates to a video prerecording method for realizing video monitoring based on file cache and application of the method. The method sets the unit time of video data as X and sets the prerecording unit data volume of the video data as 2X. The method comprises the following steps of S1.writing a prerecording file A of a first unit data volume into a disk, and writing a prerecording file B of a second unit data volume in parallel when the file A reaches the time X; S2.when the file B reaches the time X, writing a prerecording file C of a third unit data volume into in parallel while stopping prerecording of the file A and deleting the file A; S3.when the file C reaches the time X, starting to write the file A in parallel, stopping prerecording of the file B and deleting the file B; S4.when the file A reaches the time X, writing the file B in parallel, stopping prerecording of the file C and deleting the file C; and S5.repeatedly executing the steps S2 to S4 until the startup of recording is needed and stopping prerecording. According to the method and the application thereof, a defect that a physical memory space is limited is solved.