The invention relates to a nano-electrode for preparing hydrogen by decomposing water by using solar energy and a preparation method thereof. The nano-electrode is formed by coating nano-titanium dioxide on the surface of conductive glass; and the conductive glass is tin dioxide conductive glass or zinc oxide conductive glass or graphite conductive glass. The preparation method of the nano-electrode of the invention comprises the following steps of: 1) ultrasonically cleaning the conductive glass by using water and ethanol and then drying the conductive glass; and 2) reacting tetra-n-butyl titanate or titanium tetrachloride serving as a precursor and cetyl trimethyl ammonium bromide serving as a template with sodium hydroxide, wherein the mol ratio of the tetra-n-butyl titanate or titanium tetrachloride to the cetyl trimethyl ammonium bromide to the sodium hydroxide is 1-3:0.5-1.2:0.5-1.2, placing the dried conductive glass into solution, taking the conductive glass out after standing reaction, ultrasonically cleaning the conductive glass by using the water and the ethanol, then drying and sintering the conductive glass to obtain the composite electrode material coated with the nano-titanium dioxide, wherein the coating thickness is 0.5 to 4 mu m. The preparation method of the invention has the advantages of realizing the doping of nano-materials, promoting the effective separation of electron holes and improving the photocatalysis efficiency of electrodes.