Wireless Sensor Networks (WSNs) have attracted more attentions in recent years due to its low cost and convenience. Despite the great potential, power supply seriously restricted the application of WSNs. Especially in the environment such as rural areas, underground and underwater structures, the electrical wire or battery increases the cost of installation and brings the unexpected inconvenience. In this paper, a radio frequency (RF) powered far-field battery-less wireless sensor network is presented to overcome such limitation of electrical wire and battery in WSNs. In addition, mesh network approach is proposed to solve the data collision issue caused by the discontinuous power supply of far-field battery-less. Several experiments have been performed to test the performance of the system in a complex indoor environment. Results obtained verify the feasibility and reliability of this WSNs.