The effect of Pr substitution for Dy on the structure, magnetostriction, anisotropy and spin reorientation of a series of Tb0.3Dy0.7-xPrx(Fe0.9Al0.1)1.95 alloys (x=0, 0.1, 0.20, 0.25, 0.30, 0.35) at room temperature has been investigated. It was found that the Tb0.3Dy0.7-xPrx(Fe0.9Al0.1)1.95 substantially retained the MgCu2-type C-15 cubic Laves phase structure for compositions with x≤0.1 and the lattice constant increases slowly with increasing x. The magnetostriction of the Tb0.3Dy0.7-xPrx(Fe0.9Al0.1)1.95 alloys decreases drastically with increasing x and the magnetostrictive effect disappears for x>0.2. However, the magnetostriction shows a slightly bigger value at x=0.1 than the free alloys and is saturated more easily with the magnetic field H, showing that a small amount of Pr substitution is beneficial to the decrease in the magnetocrystalline anisotropy. The spontaneous magnetostriction λ111 increases linearly with incresasing x， whereas the spin reorientation temperature increases first and then decreases rapidly. The analysis of the Mssbauer spectra indicated that the easy magnetization direction in the {110} plane deviates slightly from the main axis of symmetry with the increase in Pr concentration x， namely the spin reorientation. Compared with the Al substitution，the effect of Pr substitution for Dy on the spin reorientation is smaller.