Underwater plasma acoustic source has many advantages and wide applications, but its properties are greatly affected by the trigger switch. In this paper, the working principles of two types spark gap switch (Fig.1) were analyzed. Four aspects of the performance parameter including switching delay, delay jitter, voltage-drop percentage and transmission efficiency of the trigger switches (see Table 1) were researched by test and measurement. Experimental results show that: in normal condition, with the increase of charging voltage, switching delay time td and delay time jitter for both spark gap switches will decrease. Meanwhile, the switching delay and delay jitter of type A were always greater than type B; but, the transmission efficiency of type A was 20% higher than type B. The result will guide the experiment of underwater plasma acoustic source and the design of new trigger switch.