This study introduced a self-developed wet scrubber/plasma reactor (WSB/PR) system to treat cooking fumes, and measured the changes in the optical emissions spectra (OES), before and after treatment using OES, in order to understand the changes of OES in a gaseous phase from waste gas. In terms of operational parameters of the experiment, the scrubbing solution used in WSB was tap water and an enzyme scrubbing solution, and atmospheric pressure plasma was applied inside PR. Furthermore, five different output powers (0.112 kJ/m3, 0.129 kJ/m3, 0.138 kJ/m3, 0.146 kJ/m3, and 0.156 kJ/m3) were utilized to conduct experiments. The experimental results showed that, through the operations of five different plasma output powers, active species C, C2, CH, N, Hγ, N2, N2+, NO, C+, NH, O2+, H2, and O can be tested under the following three situations: (i) start PR (plasma background value) without importing cooking fumes; (ii) cooking fumes pass through WSB/PR; and (iii) cooking fumes pass through ESB/PR. When cooking fumes are treated with WSB/PR, light emission intensity intensifies with increased plasma power, from 0.112 kJ/m3 to 0.146 kJ/m3. The same tendency occurs in the situation of cooking fumes treated with ESB/PR, which increases plasma power from 0.112 kJ/m3 to 0.138 kJ/m3. In addition, the number of active species is reduced when plasma power is increased. This indicates that, electron energy is reduced due to the H2O decomposition function in the plasma reaction, which results in a decrease in the number of active species.