Pollution of water resources caused by organic dyes, especially rhodamine B, has become one of the major environmental challenges due to its chemical stability and high toxicity. In this study, GO-PEI/CuFe₂O₄ nanocomposite was synthesized as a magnetic photocatalyst using the precipitation and self-assembly method and its performance in the photocatalytic degradation of rhodamine B under visible light irradiation was investigated. The structure and morphology of the nanocomposite were characterized using XRD, FTIR and TEM tests. Then, the effects of operating parameters including solution pH, initial rhodamine B concentration, catalyst amount and irradiation time on the degradation efficiency were evaluated and The effects of operating parameters, including solution pH, initial RhB concentration, catalyst amount, and irradiation time, were investigated using a one-factor-at-a-time approach, and the best-performing conditions within the investigated ranges were identified. The results showed that The best performance within the investigated conditions was obtained at pH 6, an initial RhB concentration of 6 mg/L, a catalyst amount of 0.1 g/L, and an irradiation time of 90 min, resulting in a degradation efficiency of about 94%. Repeated experiments with small standard errors confirmed the high reproducibility and reliability of the process. Also, the reusability of the photocatalyst showed that after five consecutive cycles, the degradation efficiency remained around 87%, indicating its good stability and effective recyclability. The results of the phytotoxicity test also showed a reduction in the toxicity of the treated effluent and an improvement in lentil seed germination compared to the original sample. Overall, the GO-PEI/CuFe₂O₄ nanocomposite, with its high degradation efficiency, recyclability and reusability, and reduced effluent toxicity, is considered a suitable option for the removal of colored pollutants from aquatic environments and application in wastewater treatment processes.