Computed tomographic technigue is use for determine mineral content of the bone. Since. H value of the voxel represents absorption of each component of photon energy spectrum knowing photon interaction cross-section and its energy spectrum we were able to derive a theorical formula to predict bone mineral content. We have used dual energy CT 96 KVp and 125 KVp for a better correlation between calculated bone mineral and actual bone mineral content. Extremely good correlationship <r=0.996> was observed between our predictive value and actual measurement of mineral content of the animal bones. Our dual energy photon method is considered of more value when fat content of the bone is considerable in our phantom study upto 40% error in mearsuring mineral content in predicted is single energy photon method is used while only $pm$2% error is predicted if dual energy method is adopted.