Abstract: Treating wastewater using electrical discharge plasma has attracted a great attention in research areas. Due to the diversity of plasma wastewater treatment reactors, evaluation indicators are needed to compare the efficiency of different reactors. This would be a great impetus to further development and improvement of plasma wastewater treatment reactors. By analyzing two widely used indicators, G₅₀ (energy efficiency) and E_TOC (TOC removal energy efficiency), and their relationship, it was revealed that although they could represent the efficiency of wastewater treatment reactors to some extent, short comings still existed in these two factors, such as the lack of limiting reaction conditions, the uncertainty of target pollutants and the imperfection in selecting evaluation parameters. Besides, the correlation between the two factors was low (R²<0.1), indicating that only one of them was not sufficient to express the reactor efficiency. Thus, considering the type of target pollutants and treatment time, an evaluation indicator, E_T, was proposed to evaluate the energy efficiency of plasma wastewater treatment reactors. This indicator was based on the removal rate of TOC per input power when 50% TOC was degraded (phenol was suggested as the target pollutant), and thus provided a more convenient way to compare the energy efficiencies of different reactors in the same condition.