PE is modified basically with inorganic matter (generally CaCO3) and some auxiliaries, but because of the interattraction of the particles, CaCO3 is easy to agglomerate, so we must add some dispersants(generally stearic acid ) ,but some study suggested that, with stearic acid , tensile strength, yield strain and ultimate elongation reduced. But we find that adding dicumyl peroxide and Maleic Anhydride can make up for the defects even increase these properties. As initiator and crosslinker ,dicumyl peroxide is usually used in synthesis of polymers. And is also Maleic Anhydride. However,in this experiment, we add a certain amount of them, dicumyl peroxide initiated Maleic Anhydride to ingraft, also,it initiated the molecular chains of PE to be cross-linked. So, the tensile properties of HDPE–calcium carbonate composites increased obviously, nevertheless ,we must add appropriate amount, if exceeded ,the mechanical properties would reduce.