Composite organic-inorganic hydrophobic silica films were made by the sol-gel method using tetraethyl orthosilicate (TEOS) and methyl triethoxysilane (MTES) as the precursors, a little n-octylamine as the catalyst, and polydimethylsiloxane (PDMS) (method 1) or silane coupling agent KH570 (method 2) as the organic modifier. Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and water contact angle (WCA) were used to analyze the chemical components, surface morphological structure and hydrophobicity of silica films on brick surfaces. The reinforcement effects on the bricks were verified by testing their variations in appearance, water absorption and porosity before and after being reinforced. The result shows that silica sol with -CH₃ group could be obtained using both of the two methods. In addition, the water contact angles treated by both methods (method 1:mass ratio of PDMS to the precursors is 10%; method 2:mass ratio of MTES to TEOS is 2) exceeded 140. The capillary water absorptivity was reduced to 1~2% the rate for the untreated bricks, while the color difference and gloss was little changed for the reinforced bricks. However, the conservation effect of method 2 is better than method 1 in terms of weathering resistance according to a relevant test, indicating that the hydrophobic silica films synthesized by method 1 should be selected as the reinforcement material for bricks.