Wind power generation occupies an important position as a new non-fossil energy in recent years, and the plant scale has been rapidly expanding as wind-farm. Since they are often built in topographically inconvenient places, the remote monitoring system has been required. Ethernet had been said to be unsuitable to the industrial network, it is one of the strong options because of its low cost and easiness to apply. In this case, it is important to secure the throughput enough for updating the data of numerous wind turbines within a fixed time. In order to achieve this, we adopted User Datagram Protocol/Internet Protocol (UDP/IP) and the multi-thread method to make the overhead of software small as possible. This paper presents the scheme of powerful network using Ethernet with multi-thread and multi-cast. The relation between the number of threads and total throughputs of network is clarified. The design procedure to derive the optimum number of threads is shown. And it is demonstrated that this scheme provide the local network of wind-farm with sufficient performance.