The present invention designs an implementation method for a virtual file system of simulating a cloud storage device. The method comprises: taking an ext3 file system of Linux as a basis, extending a physical structure of data storage of the system; according to an incoming parameter when a file is mounted, calculating a relative configuration threshold to enable the ext3 file system to be the same as a common file system within a configuration threshold range when starting writing, and when the configuration threshold is exceeded, only writing metadata information and not writing data information, so as to utilize finite physical devices to simulate a huge memory capacity.