The invention relates to a portable air purifier. An air filtration and purification unit which at least comprises one or more filter elements, a fan and an air speed control unit are arranged in the shell of the purifier, wherein air is absorbed from an air inlet at one end of the shell by using the fan; most harmful foreign matters in the air are filtered out and purified by using the air filtration and purification unit so as to obtain air with high purifying effect; the purified air is led out from an air outlet at one end of the shell; the air outlet is connected with a duct; and the other end of the duct is provided with a nostril plug capable of being inserted and sleeved in nostrils, so that the air speed of the purified air can be regulated in a driving mode or in an automatic or manual mode by using the air speed control unit, the purified air is directed led in the nostrils under appropriate air pressures, and users can easily breath pure air. Due to the design, the portable air purifier can be used for sporters, patients, pedestrians, outdoor activity personnel, persons living or working in epidemic areas, medical personnel, fire fighters and militaries and the like.