The invention discloses a downhole movable slurry casting device and method. The device comprises a caterpillar-band chassis mechanism, a slurry casting mechanism and a monitoring module; the slurry casting mechanism comprises a feeding structure and a slurry preparing mechanism, the caterpillar-band chassis mechanism comprises a chassis, a caterpillar band and a caterpillar band driving module, and the monitoring module comprises a main controller, a feeding monitoring module, a water inlet monitoring module, a motor power supply control module, a first wireless radio frequency module and a liquid crystal touch screen. The method comprises the following steps of 1, building a mine map and moving the caterpillar-band chassis mechanism; 2, checking and connecting the slurry casting mechanism; 3, preparing and delivering the slurry through the slurry casting mechanism. The downhole movable slurry casting device is reasonable in design and easy to operate; the movement of the caterpillar-band chassis mechanism drives the slurry casting device to move, and labor and material resources are saved; by monitoring the aqueous slurry in real time, the concentration and mass of the slurry areensured, and the practicability is high.