Monolithic catalysts with high catalytic activity bring about increasing interest in practical environmental purification field for volatile organic compounds (VOCs) degradation with low pressure drops. Monolithic CoMnAlO catalysts with varied Co/Mn molar ratio derived from in situ supported layered double hydroxides (LDH) film are prepared through ammonia hydrothermal growing on Al substrate following calcinations. The textural properties for CoMnAlO catalysts with low temperature reducibility, surface element species are controlled by tuning the initial Co/Mn molar ratio verified through H-2-TPR and XPS spectra. CoMn2AlO film sample shows best activity with the temperature for 90% benzene decomposition (T-90) around 238 degrees C with space velocity 300,000 ml g(cat)(-1) h(-1). The reaction rate of CoMn2AlO film is about 1.32 mmol g(cat)(-1) h(-1) at 260 degrees C with T-99, which is nearly two times to that of Co3AlO film catalyst with 0.73 mmol g(cat)(-1) h(-1), because of the higher Mn4+/Mn3+ and Co3+/Co2+ atomic ratios and reducibility inducing by the synergistic effect of Co and Mn. The value is five times higher than CoMn2AlO powder catalyst with 0.26 mmol g(cat)(-1) h(-1), which is due to the great exposure active sites.