This work focuses on the development of catalytic membrane with gold nanoparticles (Au NPs) as the active phase for a comparative assessment of continuous flow catalytic reduction of 4-nitrophenol (4-NP). However, Au NPs are prepared in a way that relies mainly on toxic reagents and immobilization on the membrane surface is still dominated by deposition, which poses a risk of leakage. We reported a green method to immobilize and reduce Au NPs on membrane surface in situ using polymer brushes containing catechol groups. Scanning electron microscopy (SEM) and x-ray photoelectron spectroscopy (XPS) observations showed that the Au3+ had been reduced to Au NPs and were uniformly distributed on the PAN-PDAu membrane surface without obvious agglomeration. Under the dynamic flow mode, the PAN-PDAu membrane showed strong catalytic activity and stability for the reduction of nitroaromatic compounds. A possible mechanism the catalytic reduction of 4-NP was explored via density functional theory analysis, electron paramagnetic resonance (EPR) and liquid chromatography-mass spectrometry (LC-MS), which verified that the catechol groups contributed to the catalytic reduction reaction of 4-NP. In addition, the PAN-PDAu membrane also had an excellent antibacterial performance. This study provides new insights for the green design of catalytic membrane for industrial applications.