The invention provides a thermal uniformity compensating method and apparatus. The steps of the method includes: respectively measuring a plurality of first resistances of a plurality of hot spot patterns of a chip over an hot spot effect, wherein a plurality of pattern densities of the hot spot patterns are different; respectively measuring a plurality of second resistances of each of the hot spot patterns of the chip by a plurality of test keys over the hot spot effect, wherein a plurality of distances between the test keys and the corresponding hot spot pattern are different; establishing a look-up information according to the first and second resistances; analyzing a layout data of the chip for obtaining a pattern density information; and generating a calibrated layout data according to the pattern density information and the look-up information.