The present invention relates to a Cracking Catalyst composition for cracking of heavy hydrocarbon feed stocks and process for preparing the catalyst. The catalyst is prepared by incorporating 1-10 wt % phosphate treated USY zeolite in which phosphate is present in the range of 10 to 50 wt % on the basis of phosphated zeolite, in a mixture of 10-50 wt % dispersible alumina, 0-30 wt % non-dispersal alumina, 5-30 wt % colloidal silica, 15-50 wt % clay and 5-15 wt % phosphate.