Nanchang Honggu Tunnel is a longest inland underwater tunnel in China. The floating transportation of tunnel segment is difficult. Two tug formation schemes for tunnel segment floating transportation are made for tunnel segment undocking, downfloating and turning based on water resistance calculation results. The tunnel segment floating transportation monitoring system based on C# and WFP technologies is designed. The remote monitoring is realized by setting RTK CPS, DGPS and inertial navigation devices on tunnel segments and tugs. The successful floating transportation of segments of Honggu Tunnel indicates that the monitoring system is reliable and effective.