The crystal structure, superconducting and magnetic properties of Pr0.2Yb0.8-xLaxBa2Cu3O7-δ have been investigated. The res ults show that with the concentration of Pr being constant, the critical transition temperature Tc of this syster decreases with the increasing of La concetration and Tc is quenched at x = 0.6. The coefficient of electron specific heat and the density of states N(0) inferred from magnetic measurements also decrease with x. The relation between the effective radii of rare earth elements and hybridization is discussed in brief.