The present invention discloses a corrosion resistant paint for the inner surface of radiator and a preparation method thereof, and belongs to the field of paints and paints preparation technology. The paint comprises, by weight, modified acrylic resin 10-80 parts, pigment 5-50 parts, filling material 5-50 parts, diluent 5-60 parts, auxiliary agent 0.1-10 parts, and other resin 0.1-10 parts. The preparation method is as follows: weighing modified acrylic resin, pigment, filling material, auxiliary agent and other resin according to weight parts; stirring the above materials and a diluent together completely by using a high speed stirrer; grinding the mixed material fully by using a sand milling machine; and adding the diluent to the mixed material by using the high speed stirrer to adjustviscosity to be 20-60 s. The said paint has high adhesion, good fluidity, and short surface drying time, thus energy cost is lowered, operation time is shortened, and the resistance to high temperature alkaline water of the paint is obviously increased.