Pure-perovskite 0.64Pb(Ni1/3Nb2/3)O-3-0.36PbTiO(3) (PNNPT) powder has been successfully synthesized by only one-step calcination using a coating method. SEM photograph shows that PNN-PT powder with the size of 2-4 mum is cubic and well dispersed. Based on X-ray diffraction analysis, solid-state reactions in the process of calcination in PbO-Nb2O5-TiO2-NiO system are investigated. In comparison with conventional solid state method, the single-calcination synthesis mechanism of pyrochlore-free lead-based niobate ferroelectrics using a coating method is tentatively proposed. A typical coating structure of Ni precipitate-coated Nb2O5 powder facilitates the formation of perovskite PNN-PT phase at a relatively low calcination temperature, resulting in the successful synthesis of pyrochlorefree PNN-PT powder in one-step calcination at 900degreesC.