The invention discloses a surface treatment method of nano calcium carbonate for an impact-resistant automobile chassis coating, which comprises the following steps of diluting lime milk to obtain slurry, regulating the specific gravity, and carbonating the slurry in a carbonating tower, measuring conductivity through an instrument, adding a crystal form control agent at the lowest point of gelatinization conductivity at the initial stage of carbonization, and stirring to react until the pH value is less than or equal to 7 to obtain calcium carbonate suspension, carrying out oleophylic surface treatment on the calcium carbonate suspension, stirring, and adding a compound treatment agent consisting of a sodium stearate saponification solution and flaxseed gum, polyhexamethylene glycol, sodium dodecyl benzene sulfonate and isopropyl triisostearoyl titanate for surface treatment, and carrying out filter pressing, microwave vacuum drying and sieving to obtain the nano calcium carbonate. The nano calcium carbonate particles prepared through the method are regular in morphology, have the advantages of being good in stability, good in rheological property, high in impact resistance, low in moisture absorption capacity and the like, and can improve the impact resistance and sagging resistance of PVC paste when applied to filling of the automobile chassis coating PVC paste.