ICP-AES was used for the direct determination of 15 rare earth elements in synthetic solutions and real sample. Spectral interferences between REEs in the mixtures of rare earth were investigated with a high-resolution echelle spectrometer and suitable analytical lines of 15 rare earth elements were selected. The Multicomponent Spectral Fitting(MSF) models were made. The method was used to remove spectral interferences and background. The factors influence the modes were discussed. The influences of acidity and ICP parameters were investigated. The compromise rendition of simultaneous determination of 15 REEs was selected. Axially viewed ICP torch was used to detemine 15 REEs,The detection limits are Y 0.21 mu g.L-1, La 9.1 mu g.L-1 Ce 14.1 mu g.L-1, Fr 1.9 mu g.L-1, Nd 7.8 mu g.L-1, Tm 0.37 mu g.L-1, Yb 0.12, Lu mu g.L-1, Ho 0.06 mu g.L-1, Er 0.06 mu g.L-1, Tb 0.53 mu g.L-1, Sm 1.14 mu g.L-1, Eu 0.09 mu g.L-1, Dy 0.08 mu g.L-1, Gd 0.30 mu g.L-1. The recoveries of this procedure are between 98.4% and 101.7%. The RSD is within 2%. The method is rapid and accuracy.