The invention discloses a smoke dust automatic collecting device for a biomass boiler. The smoke dust automatic collecting device for the biomass boiler comprises a dust collecting hopper, and a power supply, a controller and a suspending torque sensor are arranged on the outer side of the dust collecting hopper. A dust inlet port is formed in the top of the dust collecting hopper, spraying heads are arranged on the dust inlet port, and a spraying tube is connected outside the spraying heads. A magnetic valve is arranged on the spraying tube, a dust discharging port is formed in the bottom of the dust collecting hopper, and a horizontal baffle is arranged on the dust discharging port. One end of the horizontal baffle is hinged to the dust collecting hopper through a hinge, the other end of the horizontal baffle is suspended below the torque sensor through a clasp, the controller is connected with the torque sensor and the magnetic valve in a signal mode, and the controller is connected with a sound and light alarm. The smoke dust automatic collecting device for biomass boiler has the beneficial effects that the dust in the biomass boiler smoke dust collecting hopper is quantificationally discharged, the humidification of dust in the biomass boiler smoke dust collecting hopper can be quantificationally conducted, dust pollution in the dust discharging process of an original smoke dust collecting hopper is reduced, storage and conveying after dust collecting are facilitated, the labor intensity of operators is lowered, and working environment is improved.