Mass concrete temperature monitoring device and monitoring method

The invention provides a mass concrete temperature monitoring device and method. The mass concrete temperature monitoring device comprises a protection tube, a sealing bottom, a sealing opening, filling slurry, a marked line, a plurality of temperature sensors and a reading instrument. The protection tube is configured to be of a tube body structure with two through ends, the protection tube is made of heat conduction materials, and marked lines are arranged on the outer surface of the protection tube. The sealing bottom blocks the bottom end of the protection tube; the protection pipe is filled with the filling slurry, and the filling slurry is a mixture of bentonite, water and volcanic ash/fly ash; the plurality of temperature sensors are embedded into the filling slurry in the protection pipe according to set marking positions; the seal seals the opening end of the protection tube and is in detachable sealing and waterproof connection with the opening of the protection tube; the reading instrument is conne