The invention provides a viscous liquid injection device used for liquid speed bumps and belongs to the technical field of road traffic construction. The viscous liquid injection device aims at solving the problems that in the prior art, time and labor are wasted in the liquid injection process, and cleaning is not easy. The viscous liquid injection device comprises a walking unit, a liquid storage unit arranged on the walking unit and a liquid discharging unit connected with the liquid storage unit. The liquid discharging unit comprises a shell arranged on the walking unit. The shell is divided into a stirring cavity, a heating cavity and a releasing cavity from top to bottom. The stirring cavity comprises multiple spiral stirring rods, and each stirring rod is connected with a motor. Heating resistance wires are arranged on the side wall of the heating cavity. The releasing cavity is provided with a push board, the upper end face of the push board is fixedly connected with the lowerend of a push rod, the upper end of the push rod penetrates through the heating cavity and the stirring cavity to be connected with an air cylinder, multiple material leaking holes are formed in the push board, and the air cylinder drives the push board to move up and down to push viscous liquid to be discharged out of the shell.