Concerning the problems of low running speed and no response that are very likely to occur when using the common file manipulation function to dispose the large-scale result file exported from Finite Element Analysis (FEA) software, a method of data reading and writing based on memory-mapped file was proposed. By establishing the relation between disk file and process address, the file could be accessed directly to extract the data information. When the data information was very large in size, a method of piecewise map was applied to dispose the disk file, and two different forms of piecewise map were compared. Compared with the traditional method, the result shows that the proposed method can improve the speed greatly and be applied to huge text file effectively.