The nanophosphor Eu0.12Y1.78Ca0.10O3―δ was synthesized by homogeneous precipitation method under ultrasonic condition. The structures, composition and morphology of the nanophosphor Eu0.12Y1.78Ca0.10O3―δ were characterized by X―ray diffraction(XRD), energy dispersive spectrometre(EDS), inductively coupled plasma atomic emission spectrometry(ICP―AES) and transmission electron microscope(TEM). The synthesis kinetics of nanophosphor Eu0.12Y1.78Ca0.10O3―δ was investigated using differential thermal analysis and thermo gravimetric analysis (DTA―TG) at different heating rates in argon. The results show that the Eu0.12Y1.78Ca0.10O3―δ is body―centered― cubic―structured spherical nano―polycrytalline with grain size of 20nm. The precursor of nanophosphor Eu0.12Y1.78Ca0.10O3―δ is Y(OH)3 with hexagonal phase structure. The average apparent activation energy of the three reaction stages of precursor is calculated to be 102.06, 488.00 and 302.74kJ/mol by using the Doyle―Ozawa and Kissinger methods, respectively. The reaction order and frequency factor are determined by Kissinger method. The kinetics equations of each reaction stage is deduced as dα/dt=8.86×108e―12280/T(1―α)1.36; dα/dt=4.05× 1033e―58700/T(1―α)1.32; dα/dt=7.14×1019e―36410/T(1―α)1.27.