Effect of La3+-doping on energy storage performance of Pb(Lu1/2Nb1/2)O3 antiferroelectric(AFE) single crystals (abbreviated as xLa-PLN, x=1%, 3%, 5%) was studied, which is abtained by the top-seed growth method. The actual components of these crystals were 0.3%, 1.1% and 2.9% by ICP test, respectively. The crystal structure is found to be perovskite orthorhombic in nature based on the XRD analysis. In addition, two superlattice reflections are identified, which stem from the antiparallel displacements of the Pb2+ and the ordered B-site ions. The dielectric spectrum shows the variation of dielectric constant, dielectric loss as a function of temperature and frequencies, and there is no diffuse phase transition. This system shows the typical double hysteresis loops and the energy storage density gradually increases with increasing La3+ content, which can reach to 5.1 J/cm3. This is mainly because La3+-doping leads to a decrease in the tolerance factor, which enhances the stability of antiferroelectric, eventually increasing the energy density of this system.