Molybdenum based mixed oxide containing Mo0.65V0.25W0.10 was investigated for the partial oxidation of methanol. The structural property and catalytic activity of the mixed oxide catalyst was studied by surface area (BET), scanning electron icroscopy (SEM), energy dispersive X-ray (EDX), Fourier transform infra-red spectroscopy (FTIR) and X-ray diffraction (XRD). The thermal activation of the catalyst resulted increase in the conversion of methanol and the selectivity to formaldehyde. The thermal activation of the MoVW mixed oxide in nitrogen atmospheres induces partial crystallization of a Mo5O14-type oxide at 813 K. The SEM images of the thermally activated catalyst show needle like particles. These particles were agglomerates of plateletlike crystallites of a few hundreds of nanometers in size. SEM and EDX techniques show that the mixed oxide is characterized by an inhomogeneous elemental distribution on the length scale of a few microns. XRD of the thermally activated catalyst showed a nanocrystalline material identified as a mixture of Mo5O14, MoO3 and MoO2-type MoVW oxides. The catalytic activity of the MoVW mixed oxide show a good conversion of methanol and selectivity to formaldehyde.