Abstract: In order to solve problems of high labor intensity, low efficiency and easy destruction of peneumatic grasshopper trapper during unloading process, a spiral automatic unloading device was designed．It was mainly composed of enclosure, feeding hopper, central shaft, spiral blade, motor and annular force sensor system, etc．Its outer diameter of spiral blade was 200 mm, diameter of central shaft was 60 mm, pitch was 200 mm, clearance between spiral blade and enclosure was 5 mm, and speed was 90 r/min．The washer type annular force sensor with insert plate was fixed between settling chamber and feeding port of spiral unloading device, and pressure value of unloading port was set as alarm threshold of force sensor when settling chamber was filled with locusts．When force sensor test system alarmed, suction machine stopped working, and opened insert plate to drive motor and drive spiral shaft to rotate for discharging．Feeding quantity of spiral unloading device could be controlled by opening and closing size of the plate, and locusts in settling room could be avoided from directly squeezing into feeding hopper, which could provide a theoretical basis for development of automatic unloading device of grasshopper suction machine．