Abstract: An oblique flow booster fan includes an impeller having an impeller body and a plurality of blades, each blade spirally extended from top to bottom, two ends of each blade provided an upper edge and a lower edge respectively, and the upper edge having a width larger than the lower edge; an air guide assembly including an outer ring, an inner cylinder spaced apart in the outer ring, and air guide vanes evenly connected between the outer ring and the inner cylinder; a motor installed in the inner cylinder and having a rotating shaft connected to the impeller body; and a pressurization volute casing arranged outside the impeller and connected to the outer ring, one end of the pressurization volute casing provided with an air inlet, and another end of the outer ring provided with an air outlet. The fan is high wind pressure and low noise.