A method of duplicating data to multiple random accessible storage devices has steps of reading one segment of source data having multiple segments, continuously detecting newly-connected random accessible storage devices, duplicating same segments to all connected random accessible storage devices, stopping duplicating the source data to any random accessible storage device that has stored all segments of the source data and repeating the steps from the beginning. When duplicating the source data to all connected random accessible storage devices, same segments of the source data are written to all connected random accessible storage devices. Therefore, a single writing task is proceeded in each writing session. The source data can be written to all random accessible storage devices at high speed. Consequently, efficiency of asynchronously duplicating data to multiple random accessible storage devices is increased.