Ho³⁺ and Yb³⁺ co-doped La₇P₃O₁₈ up-conversion phosphors were prepared by a high-temperature solid-state process. XRD results reveal that the samples are mixtures of monoclinic structure La₇P₃O₁₈ crystals with P21/n space group and minor LaPO₄ crystals. UV-Vis DRS results indicate that La₇P₃O₁₈ crystal is an indirect semiconductor with an optical band gap of 4.10 eV. After 980 nm laser excitation, the Ho³⁺ and Yb³⁺ co-doped La₇P₃O₁₈ phosphors show the characteristic blue (486 nm), green (550 nm), and red (661 nm) luminescence peaks of Ho³⁺ ions. The peak at 661 nm dominates in the up-conversion luminescence spectra of samples. Meanwhile, with the increase of Ho³⁺ and Yb³⁺ doping content, the up-conversion luminescence intensity increases first and then decreases. By increasing the doping contents of Ho³⁺ and Yb³⁺ up to 1 at.% and 10 at.%, respectively, concentration quenching may appear by an electric quadrupole- electric quadrupole interaction process. The pumping power dependence of luminescence indicates that the green and red emissions of samples are excited by a two-photon absorption process. The color coordinates of Ho³⁺ and Yb³⁺ co-doped La₇P₃O₁₈ crystals locate in the orange-red region.