The invention discloses a nano SiO2 composite polysiloxane modified water-based terpenyl EP/PU (Epoxy Resin/Polyurethane) superhydrophobic self-cleaning polymer and a preparation method thereof. The preparation method comprises the following steps of modifying nano SiO2 into hydrophobic nano SiO2 by using trimethylethoxysilane, and then adding the modified hydrophobic nano SiO2 into a compounded system of polysiloxane modified terpenyl epoxy resin polyol aqueous dispersion and polyisocyanate under the assistance of stirring and ultrasonic waves, crosslinking and curing to obtain the nano SiO2 composite polysiloxane modified water-based terpenyl EP/PU superhydrophobic self-cleaning polymer. The surface static water contact angle of a polymer coating is greater than 150 degrees and a rolling angle of the polymer coating is smaller than 10 degrees. The preparation method disclosed by the invention is simple and convenient; a superhydrophobic coating of which the surface has a micro-nanostructure can be obtained by a spraying process; the nano SiO2 composite polysiloxane modified water-based terpenyl EP/PU superhydrophobic self-cleaning polymer is good in hydrophobicity and lasting in hydrophobic effect, and can be applied to the fields of surface self-cleaning coatings and the like.