Superconducting transition temperature and normal state resistivity of R 1 - x Pr x Ba 2 Cu 3 O 7 - δ for R = Nd, Dy, Tm, Yb and Lu were studied. Experimental results showed that Pr-substitution induced the reduce of superconducting T c and the critical Pr-substitution concentration, x c r , and normal state resistivity were related to R 3 + ion sizes. It is suggested that these ion size effects might be interpreted qualitatively by formation of the PrBa 2 Cu 3 O 7 - δ .