An electrostatic discharge protection device, comprising at least two electrostatic discharge protection units (1100a, 1100b) connected in series, wherein each electrostatic discharge protection unit (1100a, 1100b) comprises: a P-type substrate; a P-type epitaxial layer disposed on the P-type substrate; an N-type buried layer (1103a, 1103b) disposed between the P-type substrate and the P-type epitaxial layer; a first N-type well (1104a, 1104b) disposed on the N-type buried layer (1103a, 1103b) and inside the P-type epitaxial layer; a first P-type well (1105a, 1105b) disposed on the N-type buried layer (1103a, 1103b) and inside the P-type epitaxial layer, the first P-type well (1105a, 1105b) being adjacent to the first N-type well (1104a, 1104b); a second N-type well (1106a, 1106b) disposed on the N-type buried layer (1103a, 1103b) and inside the P-type epitaxial layer, and in direct contact with the first P-type well (1105a, 1105b); a doped layer (1107a, 1107b) disposed in the first P-type well (1105a, 1105b) and the first N-type well (1104a, 1104b); a first N+ region (1108a, 1108a') and a first P+ region (1109a, 1109a') disposed in the doped layer; and a second N+ region (1108b, 1108b') and a second P+ region (1109b, 1109b') disposed outside the doped layer (1107a, 1107b), wherein the second N+ region (1108b, 1108b') and the second P+ region (1109b, 1109b') are disposed in the first N-type well (1104a, 1104b) or the first P-type well (1105a, 1105b) with a conductivity type opposite to the doped layer (1107a, 1107b); wherein the second P-type well is disposed inside the P-type epitaxial layer, the second P-type well is connected to the second N-type well (1106a, 1106b) of a former electrostatic discharge protection unit, and connected to the first N-type well (1104a, 1104b) of the latter electrostatic discharge protection unit; wherein the at least two electrostatic discharge protection units are connected by a second P-type well; wherein the second N+ region (1108b, 1108b') and the second P+ region (1109b, 1109b') of the former electrostatic discharge protection unit and the first N+ region (1108a, 1108a') and the first P+ region (1109a, 1109a') of the latter electrostatic discharge protection unit are electrically connected to each other; wherein the N-type buried layer (1103a, 1103b), the first N-type well (1104a, 1104b), and the second N-type well (1106a, 1106b) are used to isolate the electrostatic discharge protection device from a protected integrated circuit, thereby preventing the device from being falsely triggered due to noise effect. a P-type substrate; a P-type epitaxial layer disposed on the P-type substrate; an N-type buried layer (1103a, 1103b) disposed between the P-type substrate and the P-type epitaxial layer; a first N-type well (1104a, 1104b) disposed on the N-type buried layer (1103a, 1103b) and inside the P-type epitaxial layer; a first P-type well (1105a, 1105b) disposed on the N-type buried layer (1103a, 1103b) and inside the P-type epitaxial layer, the first P-type well (1105a, 1105b) being adjacent to the first N-type well (1104a, 1104b); a second N-type well (1106a, 1106b) disposed on the N-type buried layer (1103a, 1103b) and inside the P-type epitaxial layer, and in direct contact with the first P-type well (1105a, 1105b); a doped layer (1107a, 1107b) disposed in the first P-type well (1105a, 1105b) and the first N-type well (1104a, 1104b); a first N+ region (1108a, 1108a') and a first P+ region (1109a, 1109a') disposed in the doped layer; and a second N+ region (1108b, 1108b') and a second P+ region (1109b, 1109b') disposed outside the doped layer (1107a, 1107b), wherein the second N+ region (1108b, 1108b') and the second P+ region (1109b, 1109b') are disposed in the first N-type well (1104a, 1104b) or the first P-type well (1105a, 1105b) with a conductivity type opposite to the doped layer (1107a, 1107b); wherein the second P-type well is disposed inside the P-type epitaxial layer, the second P-type well is connected to the second N-type well (1106a, 1106b) of a former electrostatic discharge protection unit, and connected to the first N-type well (1104a, 1104b) of the latter electrostatic discharge protection unit; wherein the at least two electrostatic discharge protection units are connected by a second P-type well; wherein the second N+ region (1108b, 1108b') and the second P+ region (1109b, 1109b') of the former electrostatic discharge protection unit and the first N+ region (1108a, 1108a') and the first P+ region (1109a, 1109a') of the latter electrostatic discharge protection unit are electrically connected to each other; wherein the N-type buried layer (1103a, 1103b), the first N-type well (1104a, 1104b), and the second N-type well (1106a, 1106b) are used to isolate the electrostatic discharge protection device from a protected integrated circuit, thereby preventing the device from being falsely triggered due to noise effect.