The work aims to explore intergranular corrosion accelerated testing method of brass in ammoniated medium, and clarify law and mechanism of influence of Zn content on brass intergranular corrosion susceptibility. During the experiment, intergranular corrosion process of brass surface was accelerated in electrochemical method, then corrosion products and surface morphology were analyzed by XRD and metallographic microscope, and intergranular corrosion rules of brass H70 and H80 were comparatively analyzed. During the simulation, adsorption and reaction process NH4 +/NH3 on the surface of H70/H80 grain boundaries were simulated by using DMol3 module in Materials Studio. Adsorption law and reaction energy barrier of corrosion particles on brass surface were compared to reveal the mechanism of intergranular corrosion susceptibility of brass. Experimental study showed that, in the NH4Cl solution, obvious intergranular corrosion could happen in 4 hours to the brass treated at 100 times self-corrosion current density. Main products of intergranular corrosion were [Cu(NH3)4]Cl2 and [Cu(NH3)4]Cl2, and intergranular corrosion susceptibility of brass H70 was higher than that of H80. Simulation study showed that physical adsorption of NH4 + in the NH4Cl solution would preferentially occur on the grain boundary, then NH4 + was decomposed into NH3 and H+ beyond reactive barrier of 1.15 eV (H70) and 1.17 eV (H80), respectively. NH3 was preferentially adsorbed on Zn atom being segregated on the grain boundary to form a complex, then it formed a complex with Cu on grain boundary. The Zn content on H70 grain boundary was higher than that on H80 grain boundary, thus brass H70 had higher intergranular corrosion susceptibility. This work cuts intergranular corrosion time of brass in NH4Cl solution solution from 7 days to 4 hours in electrochemical galvanostatic method. Besides, intergranular corrosion mechanisms of brass are clarified based upon quantum chemistry calculation and corrosion products analysis.