The invention relates to an iron-based alloy material for laser repair of a rotor main shaft. The iron-based alloy material comprises the following chemical components in percentage by weight: 0.30-0.35% of C, 18-20% of Cr, 0.35-0.50% of Mn, 1.50-1.70% of Mo, 0.80-1.0% of Si, 0.02% of Ti, 0.06% of V, and the balance of Fe. The method has the manufacturing steps of: firstly, manufacturing the iron-based alloy into powder, wherein the particle size of the iron-based alloy respectively selects two ranges: (1) 50-150 micrometers and (2) 100-325 micrometers; then, smelting by an electric arc furnace or a vacuum electric arc furnace, and manufacturing alloy powder on a horizontal atomizing process producing device protected by full Ar gas or full N2 gas, wherein the powder is in a uniform solid particle shape, and the content of satellite-shaped particles does not exceed 3-5%. The invention provides the iron-based alloy material for laser repair of the rotor main shaft, which has the advantages of quick repair operation, good quality, no damage to the rotor and the shaft diameter, safe and reliable running after the repair, long service life, and the like.