Nanosized particles of (La0.57Dy0.1)Sr0.33MnO3 perovskite-type oxides were successfully synthesized at relatively low calcinated temperature of 800 °C for 10 h using amorphous molecular alloy as precursor. X-ray diffraction (XRD) and electron diffraction (ED) revealed that the resulting product is of pure single-phase rhombohedral structure. From the measurements and calculation of isothermal magnetization at different temperatures, we discovered that the maximum magnetic entropy change at TC (358 K) increases near linearly with magnetic field increasing and shows no sign of saturation even under 5 T; moreover, a comparatively large magnetic entropy change with broader peak temperature range around the Curie temperature is also observed, and this good performance may be related to the large surface and interface of nanoparticles.