Aquailaria (gaharu) oils have been widely used as perfumery agent, as incense, medicine, in religious ceremonies and lately for aromatherapy applications. Scientific research works have recently described the relationship between gaharu oils usage with human cognitive properties changes whereby the research objective is to prove that the gaharu oils are having specific chemical compounds that lead to sedative effect and this was carried out with laboratory mice. However the purity of the agarwood oils is rather questionable. The oils could be blended with other oils or from a low quality type of agarwood thus affecting the consistency and the therapeutic properties of the oils itself. Therefore it is necessary to select the best type of agarwood oil for aromatherapy application so that it can provide the best positive effects to the consumers. This innovation mainly targeted to produce a series reference of relaxation index for consumer preference of agarwood oils using Electoencephalogram (EEG) concept. This system is integrated with dedicated signal processing techniques together with confirming the chemical compounds in order to recommend the best agarwood oil for the development of aromatherapy products scientifically.