<p>Ammonium sulfate in sewage environments significantly reduces the service life of concrete pipelines. To address this issue, graphene oxide (GO) was incorporated into cement-based materials in this study. By investigating the evolution of macroscopic and microscopic properties of GO modified cement mortar (GOCM) over different attack time, the deterioration mechanisms of GOCM in ammonium sulfate environments were elucidated, and the role of GO in enhancing chemical resistance was clarified. The results indicated that ammonium sulfate exhibits a synergistic degradation effect combining acidic and sulfate ion attacks. On one hand, the hydrolysis of NH₄⁺ generated H⁺ ions, significantly lowering the solution pH and accelerating the dissolution and decalcification of portlandite and C–S–H gel. On the other hand, SO₄²⁻ reacted with leached Ca²⁺ to form expansive products such as gypsum and ettringite, resulting in volume expansion and crack propagation. Moreover, gaseous NH₃ released during NH₄⁺ hydrolysis accumulated within pores, potentially exacerbating the deterioration process. GO incorporation substantially improved the mechanical performance and chemical durability of GOCM. After 120&#xa0;days of attack, the optimal GO dosage of 0.04% produced a denser microstructure that effectively hindered the ingress of aggressive ions such as NH⁴⁺ and SO₄²⁻, resulting in the lowest compressive and flexural strength losses of 3.2% and 30.1%, respectively. Compared to the control (GO-0), the compressive and flexural strengths increased by 27.7% and 127.9%, while cumulative porosity decreased by 26.6%, and the proportion of harmful pores was reduced by 22.3%. These findings demonstrate that GO effectively mitigates deterioration caused by ammonium sulfate, thereby prolonging the service life of sewage pipelines and reducing maintenance costs.</p>