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A series of the samples La1-x(Sr1-yNay)xMnO3(y=0.0,0.2,0.4,0.6,0.8,1.0)were prepared by the solid-state reaction method.Magnetoresistance enhancement and temperature stability of magnetoresistance in the system La1-x(Sr1-yNay)xMnO3 with unchanged Mn3+/Mn4+ ratio through the doping of both monovalent and divalent elements at A site were studied through the measurements of X-ray diffraction(XRD)patts,resistivity-temperature(p-T)curves and magnetoresistance-temperature(MR-T)curves.The results indicate that with the increase of Na doping amount,the peak value of MR increases,and it increases from 12.4％ for y=0.2 to 50.6％ for y=1.0 in the magnetic field B=0.8 T;p-T curves exhibit the double-peak phenomenon,which comes from the competition between the resistivity of surface phase and that of body phase; for the sample of y=0.8,MR increases slowly from 8.3％ to 9.4％ in the temperature range from 259 to 179 K,and MR is so stable in such a wide temperature range,which provides reference for the research on the temperature stability of MR.