A very cheap catalyst, a silica-supported polystannazane-copper complex (abbreviated as SiO2-Sn-N-Cu) was prepared by the reaction of the silica-supported polystannazane ligand with CuCl2 in ethanol. The results showed that SiO2-Sn-N-Cu can catalyze the oxidation of methanol to formaldehyde in high yield at mild conditions, i. e. at 40 degrees C and 1 atm of oxygen. The catalyst could be recovered and could catalyze the reaction repeatedly.