A USB drive mass storage device mainly includes a housing having a predetermined size, in which an optical fingerprint identification system is mounted for use with the USB drive. A printed circuit board (PCB) is located on an inner bottom of the housing with a universal serial bus (USB) plug projected from a front end of the housing. The optical fingerprint identification system includes an image sensing element and an optical prism located across front and rear ends, respectively, of the PCB, so that a space above the PCB provides an optical path for the optical fingerprint identification system. The housing is provided at a rear end with a pivotally connected rear cover to enable easy protection of and access to a fingerprint surface on the optical prism.