A rudder assembly, including a steering engine; an axial hollow rudder stock; a rudder blade; a gas release unit; and a tiller. The steering engine is disposed in a vessel stern. The tiller is connected to the steering engine. The axial hollow rudder stock includes a through hole. The through hole is small and disposed along the axis of the axial hollow rudder stock. The gas release unit is disposed in the vessel stern, and includes a control cabinet. The control cabinet includes a reagent storage tank, a reagent conveying hose connected to the reagent storage tank, a compressed air bottle, a pressure hose connected to the compressed air bottle, and a console. The pressure hose and the reagent conveying hose pass through the through hole of the axial hollow rudder stock, and then communicate with the cavity of the rudder blade.