Formaldehyde (HCHO) still remains the predominant pernicious volatile organic compound (VOC), endangering human health particularly in the room, thus its efficient elimination is of great importance to guarantee indoor air quality. It is highly desirable but challenging to fabricate robust catalyst for complete oxidative HCHO removal at room temperature without secondary pollution. In this report, Au decorated cobalt(Co)-doped Mg/Al layered double hydroxide (x%Au/Co-LDH) were prepared by in-situ deposition of uniform Au nanoparticles on preformed Co-LDH nanosheets. The x%Au/Co-LDH catalyst with optimized loading amount of 2 wt%(2%Au/Co-LDH) exhibited superior activity for complete oxidation of indoor HCHO into CO2, relative to the binary 2%Au/LDH sample without Co-doping and other control samples. Based on the systematic characterizations, it was suggested that the synergetic contributions from the Co-doping, decorated Au NPs, and abundant hydroxyl groups accounted for the effective oxidative HCHO removal over 2%Au/Co-LDH at ambient temperature. In particular, it was proposed that Co-doping favored the Au deposition on Co-LDHs with strong electronic interaction, which would be beneficial for oxygen adsorption and activation at room temperature. This study will not only be contributive for further development of novel catalysts towards effective catalytic HCHO oxidation at room temperature, but also provide new insights into the oxidative HCHO removal mechanisms.