The invention discloses a mounting method for an anti-separation filling-opening material sliding plate of a dry-mixed mortar tank truck. The filling-opening material sliding plate is a conical plate; a circular boss is arranged at the top of the conical plate; arc gaps are respectively formed in symmetric positions on the left side and the right side of the conical plate; material holes are uniformly formed in the conical plate; two parallel supporting rods I at the same height are welded on the dry-mixed mortar tank truck; the filling-opening material sliding plate is placed on the two supporting rods I; the front sides and the rear sides of the two arc gaps are respectively welded with the two supporting rods I; the tops of the two arc gaps are connected with supporting rods II; one end of each supporting rod II is welded on the dry-mixed mortar tank truck; an inner material sliding plate is arranged in the filling-opening material sliding plate. The same arc gaps are respectively formed at the symmetric positions on two sides of a plate body; the anti-separation filling-opening material sliding plate is simple in structure, convenient to mount and dismount and long in service life; materials can be effectively prevented from being separated, and full material filling is guaranteed.