A new A site complex lead-free ferroelectric ceramics of(1-x-y)BNT-xBKT-yBiCoO3 was prepared by a conventional ceramic sintering technique.The relation between composition and dielectric properties,dielectric properties and frequency were investigated.It was found that the dielectric constant and dielectric loss of unpoled samples is higher that those of poled samples.The dielectric constant and dielectric loss of unpoled samples decrease with the increase content of BiCoO3.The dielectric constant and dielectric loss of unpoled and poled samples increase with the content of BKT increasing.The dielectric constant decreases with frequency increasing,and the decreasing trend become slowly.The dielectric loss first decrease and then increase with increasing frequency.