A cross-domain electrostatic protection device having four embedded silicon controlled rectifiers (a QSCR structure) embedded in a single cell. Two grounded-gate NMOS transistors are embedded into the cross-domain electrostatic protection device for reducing trigger voltage of the QSCR structure. Furthermore, an external trigger circuit and a bias circuit are applied to the cross-domain electrostatic protection device to reduce trigger voltage of the QSCR structure and leakage current.