The invention relates to a chain tensioning adjusting mechanism which comprises a shell, a direct drive motor, a drive controller, a transmission device, a transmission lead screw, a first connector device, a chain and a second connector device. The direct drive motor is arranged in the shell, and the drive controller is arranged at the upper end of the shell and is connected with the direct drive motor through a line; a supporting plate is arranged on the outer side of the shell, the transmission device is arranged on the side, close to the shell, of the supporting plate, and the direct drive motor is connected with the transmission device; one end of the transmission lead screw penetrates the supporting plate to be connected with the output end of the transmission device, and the other end of the transmission lead screw is connected with one end of the first connector device; the other end of the first connector device is connected with the second connector device through a chain; and a tension sensor is arranged at the connecting position of the first connector device and the chain and is connected with the drive controller through a line. By means of the chain tensioning adjusting mechanism, automatic chain tensioning is achieved, the chain driving accuracy is improved, chain falling is prevented, the chain tensioning adjusting mechanism can adapt to the wicked work environment, and the reliability coefficient is high.