The invention discloses a multi-parameter landslide monitoring device and method based on a weak grating, and the device comprises a multi-parameter fiber optic sensor, a weak grating demodulator anda power supply device, wherein the multi-parameter fiber optic sensor is a whole sensing optical cable, which includes a weak grating water level sensor, a weak grating inclination sensor, a weak grating rope sensor and a weak grating water pressure sensor, that are located at the tail end and connected in series, and a stress strain sensing cable located at the front end; the weak grating demodulator is used to demodulate wavelength change information in the multi-parameter fiber optic sensor and transmit information externally by wired or wireless means; and the power supply device is used to supply power to the weak grating demodulator. The multi-parameter landslide monitoring device based on the weak grating provided by the invention packages the weak optical fiber gratings into various sensors through different packaging technologies according to requirements by customizing and engraving a plurality of weak grating arrays on a single optical fiber to realize the simultaneous monitoring of multiple parameters on one sensing optical cable, which is of great significance in landslide monitoring.