The invention discloses a static mixer of a vehicle urea SCR (Selective Catalyctic Reduction) system, which is characterized in that one group of fins is arranged in an exhaust pipe in a helical step manner, and the fins and the cross section of a pipe body are arranged at a certain included angle. Through calculation and analysis of special CFD (Computational Fluid Dynamics) software, the staticmixer can effectively increase gas disturbance to ensure that engine waste gas and urea drops are fully mixed through the mixer, obtain better distribution uniformity before entering an SCR catalyticconverter and fully react to reduce the content of NOx in the tail gas of a vehicle. The static mixer has a better mixing effect, small exhaust backpressure and a compact structure, is convenient forinstallation, and can be widely applied to a diesel engine exhaust pipeline with the urea SCR system.