The invention provides a powder metallurgy helical gear which is formed by compressing the following power stocks in part by weight: 100 parts of iron powder, 1.8 to 2.0 parts of copper powder, 0.5 to 0.8 part of molybdenum powder, 0.1 to 0.3 part of cobalt powder, 0.8 to 1.2 part of nickel powder, 0.5 to 0.8 part of graphite powder, 0.1 to 0.3 part of modified wood ash, 0.2 to 0.6 part of rare earth ferrosilicon alloy, 0.1 to 0.3 part of paraffin, 0.1 to 0.2 part of ethylene bis stearamide, 0.1 to 0.3 part of celestite powder, 0.2 to 0.4 part of yttrium powder, 0.2 to 0.4 part of boron nitride, and 0.4 to 0.5 part of zinc oxide. When in preparation, mixing the powder stocks stepwise firstly, and obtaining the finished product helical gear through compressing and manufacturing, sintering, heat treatment and surface treatment. The produced powder metallurgy helical gear has the advantages that the helical gear is good in abrasion resistance, high in strength and rigidity, good in machinability, is corrosion resistant and less susceptible to breakage, and has a long service life.