The invention discloses a plastic rubbish salvaging device for river surfaces. The device comprises a box body, the bottom of the box body is an opening, and floating plates are fixed to the portions,close to the two sides, of the opening of the bottom of the box body through bolts; a partition plate is embedded in the portion, close to the top end, of the inner wall of the box body, a driving motor is fixed to the portion, close to the middle, of the upper surface of the partition plate through bolts, and a drive gear is fixed to the top end of an output shaft of the driving motor; the sametransmission rod is rotatably connected to the portions, close to the top end, of the two opposite side walls of the box body, a bevel gear meshed with the drive gear sleeves the portion, close to themiddle, of the circumferential outer wall of the transmission rod, C-shaped slide rails are fixed to the portions, close to the bottom end, of the inner walls of the two sides of the box body, and rectangular slide blocks are slidably connected to the insides of slide grooves of the two C-shaped slide rails. When the device advances, resistance of water is reduced, the front ends of the two floating plates are in expanded opening shapes, and floating objects can be gathered as many as possible.