Disclosed is a method for separating aromatic compounds using a simulated moving bed (SMB) operation, characterized by injecting each raw material having a different composition into each different part of an adsorption chamber so as to improve the recovery rate. More specifically, the present invention provides a method for separating aromatic compounds for improving p-xylene separation in a p-xylene separation process, by injecting a high p-xylene mixture from selective toluene disproportionation process (STDP) and low p-xylene mixture from other processes (for example, processes of reformer, isomerization reactor and transalkylation of aromatics having 9 carbon atoms) into each different part of an adsorption chamber.