By introducing nonlocal elastic theory and Kirchhoff plate theory to plane wave expansion (PWE) method, the band structure of a nonlocal piezoelectric phononic crystal (PC) nanoplate is calculated. A complete band gap with magnitude order gigahertz (GHz) is opened. In order to investigate the characteristics of such a band gap in detail, the corresponding influence rules of thermo-electro-mechanical coupling fields, nonlocal effects and geometric parameters on band gaps are studied. During the researches, temperature variation, electrical voltage and external axial force are picked as the influencing parameters corresponding to thermo-electro-mechanical coupling fields. Nonlocal coefficient is chosen as the influencing parameter related to surface effects. Lattice constant, PZT-4 hole radius and nanoplate thickness are picked as the influencing parameters of geometric parameters. All the results are expected to be of help for nano electro mechanical system (NEMS) based on piezoelectric periodic nanoplates.