The invention discloses an online detection device for discharging speed of a primary hopper. A mounting bracket is fixedly arranged beside the primary hopper; a supporting cross beam is arranged on the surface of one side of the upper end of the mounting bracket through a connecting supporting plate, and the supporting cross beam can rotate by 180 degrees around the mounting bracket; a high-resolution camera and a structural light scanner are fixedly arranged on the lower surface of a cantilever end of the supporting cross beam through a mounting plate, and the high-resolution camera and thestructural light scanner are separately arranged at two ends of the mounting plate; an explosion-proof control box is fixedly arranged on the outer surface of the mounting bracket; and one end of a power line and one end of a data line communicate with the high-resolution camera and the structural light scanner, and the other end of the power line and the other end of the data line communicate with each port of the explosion-proof control box. By means of the device, automatic on-line detection of the primary hopper is achieved, the manual intervention is reduced, the discharging speed of theprimary hopper is accurately controlled, so that the medicine slurry is guaranteed to be poured in an optimal state and leveled in a combustion chamber, the air hole problem is avoided, and the stability of the product quality is guaranteed.