The effects of A-site equivalence and non-equivalence substitution on polarization temperature and electric field of K0.5Na0.5NbO3 lead-free piezoelectric ceramics are studied, and the results show that the ceramics sample of A-site equivalence is independent of polarization temperature and electric field, which can improve the piezoelectric constant. On the contrary, the ceramics sample of A-site non-equivalence substitution is sensitive to polarization temperature and electric field, constraining the piezoelectric properties.