A gray-scale representation method for a plasma display panel, which method includes arranging, in time sequence, a plurality of subfields each having a brightness weight and achieving gray-scale representation by a combination of the subfields, each subfield including an address period and a sustain period. In the gray-scale representation method, the number of sustain pulses for each subfield is determined so that a light generated from the difference of the number of sustain pulses between two adjacent gray scales can be greater than a light discharged in the address period, when the number of subfields for the higher one of the two adjacent gray scales is less than that for the lower one. The reversion of gray scales that occurs when the address light is increased as high as the sustain light can be eliminated to achieve correct gray-scale representation. A smoother gray-scale representation can be achieved with reduced power consumption by adjusting the difference of the number of sustain pulses between the two adjacent gray scales in consideration of the address light.