The present invention relates to an industrial high tenacity polyester fiber with superior creep properties and a method of preparing the same, and more particularly to an industrial polyester fiber having a mono-filament fineness of 5 to 15 dpf, an intrinsic viscosity of 0.8 to 1.25 dl/g, and a creep change rate of 4.7% or less, wherein the creep change rate is measured at 160° C. for 24 hours while giving a load corresponding to a strain of 3% after heat-treating the fiber at 220° C. for 2 minutes while giving a load of 1 g/d, and the load corresponding to the strain of 3% is based on a value obtained from a load-strain curve of the fiber before heat-treatment, and a method of preparing the same.