The trace Hg in natural water was electrically deposited on the surface of a high-purity copper rod which can effectively avoid the problems existed in directly analyzing aqueous solutions with plasma emission spectroscopy, such as the effect of water sputtering and atomic emissions quenching effect due to water molecules in plasma. Discharge stability is improved and the required voltage and current for stable discharge are decreased under the assistance of laser ignition in spark-induced breakdown spectroscopy (SIBS). Laser-ignition technique is able to enhance atomic emission of Hg in spark-induced plasma. The calibration curve of Hg in natural water is built with laser-ignition assisted spark-induced breakdown spectroscopy (LI-SIBS) technique under the condition of 7.5 V deposition voltage, 10 min deposition time and 4000 V discharge voltage. Detection limit of mercury reaches to 1 μg/L under current condition. There are no any additional pollution and memory effect for Hg in this rapid and sensitive technique.