The invention relates to the technical field of washing, in particular to a rotary knob component with self-locking and positioning functions. The rotary knob component is applied to controllers of household appliances such as washing machine and the like and comprises a rotary knob and a fixing base, the rotary knob is provided with a bushing, the fixing base is provided with a positioning sleeve which can be matched with the bushing, the bushing can be rotatably inserted into the positioning sleeve and is provided with an annular clamping groove, a clamping claw corresponding to the annular clamping groove is arranged on the positioning sleeve of the fixing base, and the clamping claw is clamped in the annular clamping groove when the bushing and the positioning sleeve are matched. The rotary knob component is simple in structure and assembly mode and low in production cost, and the problem of eccentricity of the rotary knob due to shaking is solved. Preferably, a height difference is formed between the lower edge of a shell and the top end of a boss, so that water is prevented from entering the washing machine even if the water enters a gap between the rotary knob and the fixing base, and the rotary knob component realizes self-locking, positioning and waterproof functions at the same time.