The thermal expansion and phase transition of solid solutions Yb 2−x Cr x Mo 3 O 12 have been investigated by X-ray powder diffraction and differential thermal analysis. The XRD patterns and the results of Rietveld refinement of Yb 2−x Cr x Mo 3 O 12 indicate that the solid solution limit was in the composition range of 0.0≤x≤0.4 and 1.7≤x≤2.0. Yb 2−x Cr x Mo 3 O 12 (0.0≤x≤0.4) has an orthorhombic structure and exhibits negative thermal expansion between 200°C and 800°C. Yb 2−x Cr x Mo 3 O 12 (1.7≤x≤2.0) crystallizes in monoclinic below the phase transition and above, transforms to orthorhombic. Both monoclinic and orthorhombic compounds Yb 2−x Cr x Mo 3 O 12 (1.7≤x≤2.0) present positive thermal expansion. Orthorhombic Yb 2−x Cr x Mo 3 O 12 exhibit anisotropic thermal expansion with the contraction of a and c axes, and the linear thermal expansion coefficients range from negative to positive with increasing chromium content. Partial substitution of Yb 3+ for Cr 3+ exhibits depressed monoclinic to orthorhombic phase transition.