This paper studies the effects of A-site non-stoichiometry on polarization degree of K0.5Na0.5NbO3 -AgNbO3 lead-free piezoelectric ceramics. In the research, through the preparation of Lead-free piezoelectric 0.96K0.5+xNa0.5+xNbO3-0.04LiSbO3 ceramics by solid state reaction and the building of polarization models of perovskite structure, effects of electric fields and different temperatures on the polarization and piezoelectric properties of ceramics are studied when x is at different values. Results show that the ceramics sample with the properly excessive A-site ions is not highly dependent on polarization temperature and electric field, which can realize effective polarization and improve the piezoelectric properties. On the contrary, the ceramics sample with normal A-site stoichiometry is sensitive to polarization temperature and electric field, easy to be broken down, resulting in ineffective polarization and lowered piezoelectric properties.