A series of polycrystal samples of La0.75Ca0.25-xSrxMnO3(x=0,0.075,0.1，0.125，0.14，0.15，0.175，0.2，0.25)was prepared.The entropy change and Curie temperature were measured under a magnetic field 1.5T.The microstructure of samples was used to explain the change of properties as Sr2+ substituted for Ca2+.Amalgamating a few of samples made the compound material suitable to employ Ericsson cycle.