The work aims to design a variable pitch screw to achieve the purpose of compacting powder and improving screw conveying efficiency to solve the insufficient material compactness and low packaging machine efficiency caused by the powder material containing gas during the screw conveying of powder. The gas volume method was used to determine the compacted density of the powder material. From the density and flow relationship during the screw conveying of the powder, the minimum pitch to reach the compacted density at a certain speed and the diameter of the screw blade was calculated. When the conveying length was determined, the design parameters of the variable pitch screw of the compact segment were calculated using the principle of equal-difference design. And three-dimensional modeling and simulation analysis were performed to optimize the designed screw. A three-stage variable-pitch screw was designed. Compared with the constant pitch screw, the material density increased by 6.541% and the screw conveying mass flow increased by 2.475%. The feasibility of using variable pitch to achieve compact powder is verified, and the screw conveying efficiency is improved. It provides a reference for the method of powder degassing during screw conveying.