The invention relates to a tunnel mechanics monitoring instrument protection device and a usage method. The tunnel mechanics monitoring instrument protection device comprises a rigid extensible sleeveand a flexible rubber protective cap, the rigid extensible sleeve includes an outer tube and an inner tube, and the tunnel mechanics monitoring instrument protection device can move in an opposite mode in the direction of the axis; a detachable winding device is installed on the outer tube, two gears are arranged on the detachable winding device, a gear groove is formed in the inner tube, the gear groove is matched with the gears, the rotating of the winding device is driven by the movement of the inner tube, and when the inner tube is pulled out to read data, the winding device is rotated topay off; and when the data is pushed back after being read, the winding device is rotated to take up. According to the tunnel mechanics monitoring instrument protection device and the usage method, the protection method of a monitoring instrument in tunnel monitoring and measurement is adopted, and the problems that instrument data line is difficult to store and easy to damage in the complex environment of a tunnel are solved. The tunnel mechanics monitoring instrument protection device and the usage method are not studied by predecessors.