Abstract: A composite catalyst, including: a) dispersed and cationic surface modifier-modified attapulgite as a catalyst carrier; and b) nano-Au as an active ingredient. The nano-Au accounts for 0.5-1.5 wt. % of the attapulgite. An average diameter of the attapulgite is 18-22 nm, and a length thereof is 100-1000 nm. A particle diameter of the nano-Au is 1-7 nm. The composite catalyst has a low activation temperature and high performance-to-price ratio, and can be used for oxidation of organic pollutants in waste gas under low temperatures and also has excellent catalytic effects on organic pollutants in waste fluid. A preparation method of the composite catalyst is also provided.