A data write/read auxiliary device and method for writing/reading data are provided. A data storage unit and a program storage unit are installed in the data write/read auxiliary device, wherein the program storage unit is for storing automatic execution program and protection program. When the data write/read auxiliary device is connected to a data processing device, the automatic execution program is executed for automatically executing programs stored in the program storage unit. The protection program is executed for executing an access process on data storage unit to judge whether driving a write/read head or not based on outcome of the access process when a file sharing software is executed for data downloading and uploading. Through the data storage unit as a buffer area of data before writing/reading data on a hard disk, the data write/read auxiliary device and method for writing/reading data can protect the hard disk.