The invention provides a powder material ton bag quantitative packing scale and a packing and weighing method. The powder material ton bag quantitative packing scale comprises a platform, a frequency-variable spiral mechanism, a weighing module, a weighing frame, an air cylinder, a fan, a lifting bag clamping mechanism, an automatic bag releasing mechanism, a chain plate conveying machine, a weighing control system and an air passage, wherein the frequency-variable spiral mechanism controls the feeding speed, the weighing module is connected with the platform and the weighing frame, the weighing frame is used for transmitting the weighing weight, and the air cylinder is arranged on the weighing frame and drives the lifting bag clamping mechanism. The powder material ton bag quantitative packing scale has the advantages that in the packing and weighing processes, the labor is saved, the automation degree is high, the automatic bag expansion can be realized, the automatic lifting, the automatic filling and the weighing control of the lifting bag clamping mechanism can be realized, the powder material ton bag quantitative packing scale can be widely applied to packing industries of different powder materials, the automation degree is high, the operation is simple, convenient and fast, the production capability is high, and the work intensity and the operation cost are low.