The invention discloses an SCR urea mixer. The SCR urea mixer comprises a shell and a urea spraying base. A first partition plate and a second partition plate are arranged at the two ends of the shell. A first flow guiding plate and a second flow guiding plate are arranged in the shell and are arc flow guiding plates. A first mixing area is formed among the first partition plate, the second partition plate, the second flow guiding plate and the shell. A second mixing area is formed among the first partition plate, the second partition plate, the first flow guiding plate and the second flow guiding plate. A heat preservation area is formed between the first flow guiding plate and the shell. The first partition plate is provided with an air inlet area corresponding to a reaction area. According to the SCR urea mixer, engine exhaust airflow can be sufficiently utilized for conducting crushing and heat exchange on urea liquid drops, a urea water solution entering the mixer is promoted to be sufficiently atomized and hydrolyzed and is sufficiently mixed with engine waste gas, and deposition and crystallization of the urea can be effectively prevented; and through the analysis from the professional CFD software, the backpressure of the mixer is low, and airflow uniformity and ammonia gas uniformity meet the requirement of the national standard VI for uniformity.