The invention discloses a practical air purifier. The practical air purifier comprises an air purifier master machine, an air purifier submachine, a first air changing module, a first gas filter, a disinfection module, and a sterilization system, wherein the air purifier master machine comprises a housing; a prefilter, an electrostatic dust collection device, a photocatalyst filter dam, a negative-ion generator and a cross-flow fan are sequentially arranged in the housing; the photocatalyst filter dam is formed by metal grilles coated with a nano-sized titanium dioxide coating; a UV illuminating lamp is arranged at the top of the photocatalyst filter dam; the air purifier master machine comprises an air quality sensor and an intelligent controller; the air purifier submachine comprises a control module and an air purification device; the intelligent controller is used for transmitting control signals to start the air purifier master machine and the air purification device in the air purifier submachine to work; the sterilization system comprises an impurity removal filter screen, a smell removal filter screen, and a sterilizer. Through the adoption of the practical air purifier disclosed by the invention, toxic and harmful gas in the air can be effectively degraded, so that the air is fresh.