Abstract: The present invention provides a method for searching a file in a file directory according to a given file name of the file. The method includes the steps of: counting number k of characters of the file name; calculating number n of files in the file directory; executing a first searching method when (2k)*>=n, including the steps of: comparing the given file name with each file name in the file directory; and opening the file if any file name matches the given file name; executing a second searching method when (2k)*<n, including the steps of: enumerating all potential file names of case-sensitive characters according to the given file name; and trying to open file with each of the potential file names. The above-mentioned p means the ratio of time consumed by opening a file with a file name over time consumed by comparing the given file name with another file name.