Abstract: A method of producing a centrifugal fan wheel without a volute casing includes a design of an outer diameter of a fan wheel and a shape design of a fan blade. The centrifugal fan wheel of the invention reduces the absolute velocity of the fan blade by decreasing an outer diameter of the fan blade to thereby eliminate a self-loss area of jet streams and attain the object of reducing noise. The invention calculates the best air outlet angle and the best air intake angle of the aerodynamic performance through mathematical derivation of aerodynamic equation and theory to thereby achieve the largest output of air volume within the smallest range of full pressure loss.