Fluoride nanoparticles of Ln3+ (Ln3+=Pr3+, Nd3+, Sm3+, Gd3+,Tb3+ Dy3+, Ho3+, Er3+, Tm3+, Yb3+)/Eu3+:LaOF and Eu3+:LaOF with rhombohedral crystal structure were prepared by a hydrothermal-sintering method. The red fluorescence emission of Eu3+ ions was found to be enhanced with most of the co-dopant Ln3+ ions. Compared with strong fluorescence emission at 610 nm of Eu3+:LaOF nanoparticles, the enhancement factors was up to ten times in Ln3+ (Ln3+=Gd3+, Dy3+, Tm3+)/Eu3+:LaOF co-doped nanoparticles. The results show that the asymmetry of the local environment of Eu3+ ion was reduced by co-doping Ln3+ ion into the nanoparticles, and that energy transfer might occur between Eu3+ and codopant Ln3+ ions, which is suggested as the source of the observed fluorescence enhancement.