It is general that with the distance increasing the communication quality of Free Space Optical (FSO) drops seriously, and the maximum transmitting distance is usually about 2 kilometers. In order to increase the covering range and transmission quality of the FSO system, a relaying device which is between the nodes is researched in the paper. In the device, the optical signal is transformed into electric signal by phototube. The device analyzes the receiving signal, acquires the effective signals and normalizes the signal waveform. Then, the reshaped signal is sent to the objective node. It can reshape, retime and regenerate signals, and the covering range can be extended. At the same time the transmission quality can also be improved. The approach is able to permit maximum transmitting distance more than 2km without deterioration of signal quality. At present, the experiment in our lab has already realized the 200m and 8M communication with the relaying technology successfully. The details are presented in the paper.