The invention discloses a 
manganese dioxide-magnetic 
biochar composite catalyst as well as a preparation method and application thereof. The preparation method comprises the following steps: 1) pyrolyzing 
biomass under anaerobic or 
oxygen-limited conditions to generate 
biochar, washing with water and 
alcohol for three times respectively, 
drying, 
grinding and sieving; 2) uniformly stirring a ferricsalt and a 
ferrous salt in an 
aqueous solution, then adding the prepared 
biochar, and then adding an alkali liquor; under heating, conveying an obtained coprecipitate into ferroferric 
oxide, and obtaining magnetic biochar; washing with watert for three times, 
drying, 
grinding and sieving; 3) adding the magnetic biochar into a 
manganese salt solution, and uniformly stirring; then adding a 
potassium permanganate solution, uniformly mixing and heating at a high temperature for a period of time. The method is simple in process, low in cost, and is capable of achieving large-scale industrial production. The prepared 
manganese dioxide-magnetic biochar composite catalyst is excellent in catalytic performance, can be applied to degradation and removal of various pollutants, is easy to recycle, and is an 
efficient catalyst.