Anaerobic membrane bioreactor is an attractive option for antibiotic pharmaceutical wastewater treatment, but the unsatisfied treatment performance and membrane fouling issue hindered its wide application. Herein, magnetic biochar (MBC) derived from peanut shells was added to AnMBR for synthetic pharmaceutical wastewater treatment containing sulfamethoxazole (SMX). The results indicated that the treatment performance was improved with 80 % of COD and over 90 % of SMX removal. This can be explained by the adsorption capacity of MBC and improved microbial activity due to the direct interspecies electron transfer enhancement with MBC addition. Membrane fouling was also alleviated due to the adsorption and magnetic bio-effect of MBC, leading to the reduced soluble microbial product (SMP) (22.2 to 6.3 mg/gVSS) and extracellular polymer substance (EPS) concentration (18.9 to 14.2 mg/gVSS), and enlarged particle size (60.6 to 113.4 μm). Microbial diversity analyses indicated that hydrolysis and acidogenesis bacteria (Bacteroidetes and Choloflexi phyla), methanogenic archaea (Methanobacterium and Methanosaeta), and bacteria related to electron transfers (unclassified_f_Geobacteraceae) were enriched due to the presence of MBC. Additionally, the SMX plausible biotransformation pathway and removal mechanism further validated that MBC addition can improve the SMX biodegradation and biotranformation. Importantly, the MBC addition facilitates antibiotic degradation and fouling alleviation of AnMBR, which makes AnMBR a more attractive choice treating for antibiotic pharmaceutical wastewater.