Pr0.3TbxDy0.7-xFe1.9Ti0.1(x=0.18-0.21) alloys were prepared by arc melting and then the samples were annealed under different conditions. Their magnetostriction was studied. The results indicate that the second phase exists in all samples before annealing and greatly influences the magnetostriction of samples. The second phase cannot be eliminated and the magnetostriction can not be improved by 700 oC, 6 d annealing. However, the second phase can be efficiently eliminated by 900 oC, 3 d annealing. In particular, for the sample of Pr0.3Tb0.21Dy0.49Fe1.9Ti0.1, the pure cubic Laves phase with MgCu2-type structure was obtained and its magnetization and magnetostriction coefficient increased. It has a high magnetostriction coefficient of about 1.12×10-3 at 900 kA/m