The invention discloses a constant weight feeder tension device, and relates to the technical field of mechanical device manufacturing. The constant weight feeder tension device comprises symmetric roller bearing seats, a machine frame and a transmission shaft arranged between the roller bearing seats. The roller bearing seats are arranged between guide rails on the upper end face and the lower end face of the machine frame respectively and connected with the machine frame through a screw rod, one end of the screw rod penetrates through one side face, perpendicular to the guide rails, of the machine frame to be fixedly connected with the roller bearing seats through nuts, and the other end, extending out of the side face of the machine frame, of the screw rod is sleeved with a cylindrical helical compression spring. Compared with the prior art, the constant weight feeder tension device is simple in structure, convenient to install, easy to operate, and capable of being automatically adjusted and effectively improving measuring accuracy.