The real-time measurement of the SCB voltage，current and plasma temperature based on the double-line method of atomic emission spectroscopy was conducted by using high-speed digital oscilloscope. The curves of SCB plasma temperature and SCB consumed energy versus time were obtained. The effects of five different capacitances (6.8，15，47，68，100 μF) on the functioning time，SCB consumed energy and SCB plasma maximum temperature were analyzed respectively when the charging voltage was 21 V. The results show that there is a linear relationship between the maximum temperatures and the capacitances. SCB plasma maximum temperature increases from 2242 K to 3324 K when capacitance increases from 6.8 μF to 100 μF.