The invention relates to a side slope optical fiber Bragg optical grating multi-point displacement sensor and a using method of the side slope optical fiber Bragg optical grating multi-point displacement sensor and belongs to the field of photoelectron measuring technologies. The displacement sensor comprises an upper end flange plate, an upper end elastic protection ring sleeve, an upper end pull rod, an upper end displacement spring, a protection steel tube, an elastic steel disc, optical fiber Bragg optical gratings, a lower connection leading-out optical fiber, an upper connection leading-out optical fiber, a steel tube optical fiber leading-out hole, a lower end displacement spring, lower end pull rod, a lower end flange plate and a lower end elastic protection ring sleeve. According to the relational expression between the displacement value Delta Lambda Beta of the central wavelength of the optical fiber Bragg optical gratings adhering to the elastic steel disc and the displacement L of the sensor, the displacement changes, caused by the displacement of side slope hole soil layers or cracking of rock stratums, of the measuring position are calculated. According to different monitoring requirements, different numbers of displacement sensors can be connected in series to achieve multi-point displacement monitoring in side slope holes; the optical fiber Bragg optical gratings are adopted, so that the anti-electromagnetic interference capacity and the corrosion resistance capacity are high; the structure is simple, and operation is convenient.