The utility model discloses a first-stage blade of an air compressor with a hub diameter of phi 762, which relates to a blade. The problem that a traditional first-stage blade of the air compressor with the hub diameter of phi 762 is unsmooth in a profile face, unstable in quality and short in service life is solved. The working part and the root of the blade are integrally formed from top to bottom; a moulded line of the blade working part is a variable-cross section twisted blade; and the cross section is gradually reduced from the root part to the top part. The cross section of the working part of the blade from the root part to the top part has the following geometric data that: the height of the cross sections from the cross section A-A to the cross section K-K is 0 to 164.12mm; the axial width is 79.6259 to 51.331mm; the chord length is 83.58 to 83.496mm; the air inlet angle is 46.967 to 31.093 degrees; the mounting angle is 71.677 to 37.46 degrees; and the maximal thickness of the moulded line is 9.964 to 3.916mm. The first-stage blade of the air compressor with the hub diameter of phi 762 is applied to an air compressor of which the hub diameter phi is 762.