We have investigated the effect of Lutetium doping on YBCO prepared by conventional solid-state reaction method by means of XRD, AC susceptibility and DC magnetization measurements and theoretical analysis. AC susceptibility measurements for sintered YBCO pellets have been performed as a function of temperatures at constant frequency and AC field amplitude in the absence of DC bias field. The critical current densities as a function of temperature have been estimated from the AC susceptibility data. DC magnetization measurements were done at 20K and 77K upon zero field cooling (ZFC) process. 50% Lu substitution for Y on YBCO superconductors improves the critical current density and lower critical field Ho at low temperature region (at 20K). (C) 2010 Elsevier B.V. All rights reserved.