Three-dimension paraffin compensator was designed to construct the tissue equivalent compensator for irregular body contours and obiliques beam incidence. The ratio of compensator thickness to tissue deficit was depended on field size, depth and air gap because the scattered dose loss. The ratio of compensator-tissue was optimized 0.79, 0.73, 0.61 and 0.56 in 6MV x-rays as function of field size $4 iems4,;10 iems10,;20 iems20;and;30 imes30cm^2$ respectively. in our study. Using this tissue equivalent compensator, it can be got $2\%$ difference of dose at same mid-plane in phantom study