[en] Nanocrystalline La_0.7Sr_0.3MnO₃ (LSO) has been synthesized by an alkali metal nitrate flux process at a relatively low temperature of 600 deg. C. Scanning electron and transmission electron microscopic images show that LSMO grains are of good crystallization and uniform size distribution. Inductively coupled plasma and elemental analyses indicate that the content of K⁺ is no more than 0.6% in all the samples and the stoichiometry of La, Sr and Mn is very close to the expected value. A significant enhanced magnetoresistance is observed in the nanosized LSMO especially at low temperatures. By improving grain crystallization, the surface spin-glass behavior disappears, and the blocking temperature corresponding to the super-paramagnetic transformation shifts to a higher temperature