A novel process for reuse of anaerobic digestion effluent in citric acid fermentation was investigated to resolve wastewater pollution in citric acid industry. Studies showed that anaerobic digestion effluent directly reused had no effect on liquefaction of raw materials, but produced inhibition for citric acid fermentation. Further experimental studies proved excess ammonia-nitrogen, Na+, K+in the anaerobic digestion effluent can inhibit citric acid fermentation and its corresponding critical inhibition concentration respectively 100, 200, 300 mg/L. In this paper, the combination of ultrafiltration and nanofiltration membrane technology was adopted to deal with the anaerobic digestion effluent, and these inhibitors have been effectively purified, including Na+, K+removal rate reached 90%, ammonia-nitrogen removal rate is over 80%. The anaerobic digestion treated by a combination ultrafiltration and nanofiltration reused in citric acid fermentation, citric acid production was 139.25±1.85 g/L，which was comparable to the control(138.70±2.46 g/L). The novel reusing process is feasible and not only reduces wastewater pollution problem and saves fresh water resources, has high economic benefit, environmental benefit and social benefit.