The piezoelectric Li doped K0.5Na0.5NbO3 ceramics,namely K0.5Na0.5NbO3+x/2%Li2CO3(KNN-xL),were prepared by the solid state reaction.The phase,microstructure and electric properties were studied for KNN-xL samples with different Li content (x being 0,0.25,0.50, 0.75,1.00, and 1.50 respectively).The results show that all samples possess perovskite structure with orthorhombic symmetry.The piezoelectric constant d33,planar coupling factor kp,mechanical quality factorQm and bulk density ρ of the KNN-xL ceramic samples increased firstly and then decreased with the x content increase.While the dielectric losses tanδ of all modified ceramics were lower than that of pure KNN.The optimum electric properties (that is d33=122 pC/N，kp=41%，Qm=115，εr=548，tanδ=0.022，ρ=4.32 g/cm3) of the ceramic sample in the composition of x=0.5 can be obtained.In addition, the phase transition temperature of the orthorhombic to tetragonal gradually decreased and the Curie temperature gradually increased withxcontent increase.