The invention discloses a rust conversion type waterborne rusty coating and a preparation process thereof. The rust conversion type waterborne rusty coating is mainly prepared from the following components in parts by weight: 30-40 parts of a copolymer emulsion, 1-5 parts of an alcohol-ether solvent, 5-10 parts of an antirust pigment, 1-3 parts of a corrosion inhibitor, 3-15 parts of a pigment, 5-15 parts of filler, 2-6 parts of hydroxyethylidene diphosphonic acid, 0.3-0.8 part of a flash-rust inhibitor, 20-30 parts of deionized water, 0.1-0.5 part of a surfactant, 0.1-0.5 part of an organosilicon defoamer, 0.1-0.5 part of a thickener, 0.5-1.5 parts of an emulsion stabilizer and 0.5-1.5 parts of a multifunctional polymer dispersant. According to the rust conversion type waterborne rusty coating, by adopting the copolymer emulsion prepared from vinyl chloride, vinylidene chloride and an acrylic emulsion as a film forming matter, VOC (volatile organic compound) emission is effectively lowered, harms to environment and a human body are reduced; and a conversion agent of the hydroxyethylidene diphosphonic acid does not erode a metal matrix and is non-toxic and harmless, so that the rust conversion type waterborne rusty coating can omit cleaning work of a rusty layer before the surface of a corrosion matrix is coated with an ordinary coating and also obtains good preservative effect.