In this paper, a two-step method is adopted to add titania (TiO2) nanoparticle and silica (SiO2) nanoparticle in commercial water-based paint to form the nano-paint with various concentrations of the added nanoparticle. The paint is sprayed onto the steel plate to form a coated film as the test samples. The experiments are implemented in order to investigate the effects of the nanoparticle on reflection spectra, surface hydrophobic and heat transfer performance of the coated film. The experimental results show that adding the nanoparticle indeed has positive effects on the above properties. This research contributes to the development of the functional paint for various applications.