The effects of calcination on the crystallinity and grain growth model for microstructure development of wormhole-like mesoporous tungsten oxide are investigated in this study. We found that residual mesopores of wormhole-like tungsten oxide can be seen calcined above 500 degrees C, as evidenced by retention of a wormhole-like mesostructure of tungsten oxide. A model was proposed to combine grain growth with wormhole-like mesoporous behavior and to investigate whether the formation of wormhole-like mesoporous tungsten oxide can retard the collapse rate of mesopores during the calcination process.