The invention relates to a type of rare earth halosilicate red long-afterglow phosphor, and a preparation method thereof. Especially, the invention relates to a type of red long-afterglow phosphor prepared from a base material of rare-earth-modified solonetz halosilicate, and a preparation method thereof. The phosphor is characterized in the structural formula of: (1-[alpha])M,2[alpha] / 3Ln)5(SiO4)2X2:[beta]Eu<3+>,[gamma]Ln<,>, wherein M is at least one of Mg and Ca, Ln is at least one of Y, La, and Gd, X is at least one of F and Cl, Ln<,> is at least one of Dy<3+>, Er<3+>, and Bi<3+>, [alpha]=0.1 to 1, [beta]=0.03 to0.07, and [gamma]=0.001 to 0.05. According to the method, solonetz halosilicate is appropriately modified with rare earth, such that rare-earth-modified solonetz halosilicate, which has a structural formula of (M,Ln)5(SiO4)2X2 is obtained. The rare-earth-modified solonetz halosilicate is adopted as a novel base material, and a rare earth ion Eu<3+> is adopted as a luminous ion. According to the luminous ion Eu<3+>, other rare earth ions or non-rare-earth ions are selected as sensitizers, such that the red long-afterglow phosphor with a main peak wavelength of 611nm, an initial luminance of 1200mcd / m<2>, an afterglow period greater than 12 hours, and a good chemical stability is obtained.