The invention relates to the technical field of weighing auxiliary equipment, especially a control instrument desk with an adjustable-back fixed support. The instrument desk comprises a top desk seatand a bottom weighing pedestal. A back bolt of the bottom weighing pedestal is fixedly connected with a hollow structure longitudinal supporting rod for connecting the top desk seat. The back of the top desk seat is provided with a plurality of lateral connection grooves. According to the invention, the back is provided with the lateral connection grooves where translation sliding blocks are disposed. Moreover, the outer sides of the translation sliding blocks are movably connected with a fixed support for the bolt fixing of the longitudinal supporting rod. The connecting angle of the fixed support is fixed through an elastic external limiting sleeve on the fixed support, thereby enabling the fixed support to freely change the connecting angle and position, facilitating the adjustment of the instrument desk, and enabling the operation to be simple and convenient.