In order to improve the detection sensitivity for the technique of laser induced breakdown spectroscopy (LIBS) of liquid matrix, the key parameters of the spectroscopic detection system must be optimized. The liquid jet sampling technique is adopted. The analysis lines of six metal elements of Pb, Cr, Cd, Mn, Ca, and Al mixed in an aqueous solution are selected. The maximization of the signal-to-noise ratio of LIBS signals for each metal element is used as the optimizing criterion. When the gate width of an intensified charge-coupled device (ICCD) is 0.3 μs, the key system parameters of laser pulse energy, ICCD gate delay and liquid sample flow rate, are optimized as 50 mJ, 2.0 μs and 40 mL/min, respectively.