RF-harvesting energy is the process of scavenging power from electromagnetic fields at radio frequency band. By RF-harvesting technology, we are able to recycle EM-fields and use them as power supply for electrical devices. The significant advantage of this technology is the reduction of electromagnetic pollution existence in the free space from wireless radio networks, cell phone towers, TV signals, and etc. An important component in RF harvesting system is the "rectenna". The rectenna is composed of a receiving antenna and a RF/DC converter. Since the receiving antenna provides the RF power as input for the converter, the design of a receiving antenna with high efficiency represents the objective of the present paper.In order to design antenna and to improve the link coupling, a hybrid optimization method in this study, called Genetical Swarm Optimization (GSO), is proposed and applied. The GSO has already been successfully applied to the optimization of antennas, wireless systems, and energy harvesting devices.