The process evaluation of zinc oxide nanoparticle (ZnO NP) was added to enhance the degradation of petroleum wastewater (PWW) fermentation system with different mixing ratios for enhancing methane production. The results showed that the highest methane yield and total solids (TS) removal ratio reached 485 mL/g-VS L PWW added and 81.9% at the ZnO NP g-VS L PWW ratio of 4.5:15, respectively. The proposed model CO2 sequester 545 mL CO2/L PWW, production rate 750 mL CH4 g-VS L PWW/h, and CH4 yield was 4.85 L CH4 g-VS L PWW at 4.5:15 of ZnO NP g-VS L PWW. The kinetic analysis indicated that the modified Gompertz model best fitted the actual evolution of methane yields, as evidenced by the low root mean square prediction error (RMSPE) as well as high correlation difference between (Diff.%) the predicted and actual values. The parameters analyses were highlighted that the PWW digestion with ZnO NP substantially enhanced the hydrolysis rate (k(hyd)), methanogenesis potential (f(d)), lag phase time h (lambda), and methane production rate (Rm) of PWW. The evolution of soluble metabolites, utilization of ZnO NP and carbohydrates were also improved by co-fermentation.