The invention discloses a multi-section type adjustable mechanical grabbing device comprising a base plate, a sliding rail arranged on the base plate, and a rodless air cylinder arranged on one side of the sliding rail and parallel to the sliding rail. A sliding rail connecting block is slidably arranged on the sliding rail and fixedly connected with an up-down air cylinder mounting plate; an up-down pushing air cylinder is mounted on the up-down air cylinder mounting plate; an adjusting connection plate is arranged on the up-down pushing air cylinder; one end of the adjusting connection plateis fixedly connected with a transverse adjusting plate; a longitudinal adjusting plate is slidably arranged on the transverse adjusting plate; and a suction nozzle is slidably arranged on the longitudinal adjusting plate. By adopting the technical scheme of the multi-section type adjustable mechanical grabbing device, substrates can be grabbed conveniently and effectively, the transverse and longitudinal sizes of a mechanical arm can be adjusted so as to grab the substrates of different sizes, the structure is simple, movement is stable, and reliability is high.