A method for enhancing performance of data access between a personal computer and a USB Mass Storage is provided. The personal computer is equipped with a plurality of layers of drivers regarding USB data access, and a lower layer of the layers of the drivers includes a USB Bus Driver. The method includes: monitoring commands sent from an operating system (OS) file system to an upper layer; and when a command sent from the OS file system to the upper layer is utilized for accessing data of a data amount that is greater than a predetermined threshold value, omitting a portion of a plurality of IRPs, automatically generating a plurality of replies for replying to the omitted IRPs, and altering at least one IRP of remaining IRPs in order to correctly access the data with a lower IRP count, wherein the plurality of IRPs is associated with the command.