The invention discloses a cyclone separator for fine dust. The cyclone separator comprises cyclone cylinders and inner cylinders located in the cyclone cylinders. A dust-blocking and air-ventilating component is arranged at an air inlet of each inner cylinder, and/or an air-blocking and dust-discharging component is arranged at a dust outlet of each cyclone cylinder. The dust-blocking and air-ventilating components are blade type dust-blocking and air-ventilating components or hole type dust-blocking and air-ventilating components or screen type dust-blocking and air-ventilating components. The air-blocking and dust-discharging components are convex-face air-blocking and dust-discharging components or planar air-blocking and dust-discharging components or concave-face air-blocking and dust-discharging components. The dust-blocking and air-ventilating components are fixedly connected with the inner cylinders, and the air-blocking and dust-discharging components are fixedly connected with the cyclone cylinders. The cyclone separator for fine dust can effectively remove fine dust in smoke under the condition that a second-stage cooling device and a third-stage cooling device are omitted, and more useful clean high-temperature hot smoke is obtained; and meanwhile, compared with a bag dust collector, the manufacturing cost of equipment is greatly reduced.