The invention relates to a negative pressure cyclone feeding device for producing ammonia sugar from chitosan, relating to the technical field of feeding devices for producing ammonia sugar from chitosan; the negative pressure cyclone feeding device comprises a conveying pipeline connected with the discharge port of a crushing machine; an impurity removing composite pipeline is connected at the other end of the conveying pipeline; the upper end of the impurity removing composite pipeline is connected with the feed port of a cyclone separator; the middle part of the impurity removing composite pipeline is connected with an impurity outlet pipe; the impurity outlet pipe is connected with a switch valve; the lower end of the cyclone separator is provided with a discharging airlock; the top of the cyclone separator is connected with a wind pipe; the wind pipe is connected with a pipeline through a centrifugal draught fan; and the other end of the pipeline is connected with the feed port of a dust cleaner. The device is simple in structure and advanced in technology; the whole device is in a combined type, and is convenient to mount and dismount and low in use cost and maintenance cost; the impurities such as stone blocks and the like are separated from the impurity port; the manual sorting operation is reduced; the degree of automation is high; the device feeds the material in a negative pressure manner, thereby preventing the disordered scattering of materials, dust and the like in the feeding process; and the environment of a workshop is clean.