A pH-responsive system was prepared by using a magnetic nanocomposite, folic acid-conjugated chitosan (FA-CS) grafted Fe3O4/GO, and then used for loading and controlled release of an anti-cancer drug, gemcitabine (GEM). The successful synthesis of FA-CS/Fe3O4/GO was confirmed by various characterization techniques such as FE-SEM/ EDX, TEM, FT-IR, XRD, TGA, VSM, and BET. The nanocomposite had a mesoporous structure with the specific surface area of 68.96m2 g-1, the pore volume of 0.25 cm3 g-1, and the mean pore size of 14.78 nm. The optimum conditions for drug loading through adsorption were found to be pH=4, adsorbent dosage of 0.5 g L-1, temperature of 298 K, and contact time of 45 min. Experimental data indicated that GEM adsorption onto FA-CS/Fe3O4/GO has a satisfactory correlation with the pseudo-second-order kinetic and Freundlich isotherm equations. The maximum adsorption capacity of GEM was 221.17mg g-1 for FA-CS/Fe3O4/GO, which was quite higher than the non-functionalized Fe3O4/GO with the value of 33.99mg g-1. Furthermore, the in-vitro drug release profile of GEM from drug-loaded FACS/ Fe3O4/GO was studied within 48 hours at 37 ℃, and the results indicated a higher drug cumulative release amount in simulated cancer fluid (pH 5.6) compared to simulated human blood fluid (pH 7.4). Also, the Peppas-Sahlin kinetic model best fitted the release kinetics data. The result of drug release implied that FA-CS/Fe3O4/GO magnetic biocomposite could be a potential carrier for the sustained and controlled release of GEM.