The invention relates to electronic ballast for a high pressure sodium lamp. The electronic ballast for the high pressure sodium lamp comprises an EMI circuit, a full bridge rectifying circuit, a half bridge inverter circuit and a trigger starting circuit, wherein the EMI circuit carries out filtering on input alternating current power, the full bridge rectifying circuit carries out rectification on output signals of the EMI circuit, the half bridge inverter circuit inverts output signals of the full bridge rectifying circuit into low-frequency sine waves and supplies the low-frequency sine waves to the high pressure sodium lamp, and the trigger starting circuit provides trigger signals for the high pressure sodium lamp and lights up the high pressure sodium lamp. The electronic ballast for the high pressure sodium lamp further comprises a protection circuit which is connected with the half bridge inverter circuit and provides open circuit protection and short circuit protection for the high pressure sodium lamp. The electronic ballast for the high pressure sodium lamp has the advantages of being simple in circuit structure, low in cost and long in service life, is suitable for large power products and free of sound resonance phenomena, and has wide adaptability.