The invention discloses an adjustable vibration screen net tensioning mechanism which comprises a screen box, screen net connection plates, tensioning grooves, connection rods and a pull rod. The tensioning grooves are formed inside the two sides of the screen box. The left end and the right end of the screen box are provided with a feed inlet and a discharge outlet correspondingly. The screen net connection plates are arranged inside the tensioning grooves and connected with a screen net. The rear ends of the screen net connection plates are connected with the connection rods. The other ends of the connection rods are connected with adjusting knobs. Springs are arranged between the tensioning grooves and the screen net connection plates correspondingly. The bottom of the screen net is connected with the pull rod. The lower portion of the pull rod is provided with an external thread. The external thread is matched with an internal thread hole formed in the bottom of the screen box. A bottom knob is fixed to the bottom end of the pull rod. An anti-skid gasket is arranged between the bottom knob and the screen box, and anti-skid gaskets are arranged between the adjusting knobs and the screen box. According to the adjustable vibration screen net tensioning mechanism, the structure is simple, use is convenient, stretching of the two sides of the screen net is matched with tensioning of the bottom of the screen net, the whole screen net is tensioned, and the tensioning degree can be adjusted by the adjusting knobs.