Three-dimensional (3D) carbon nanotube networks (CNNW) have been successfully constructed by a simple solution route for the first time. The as-obtained networks consist of the ordered alignment of nanotubes cross-linked with a joint-angle of approximately 90o. Also, the joint points in the networks are very stable and the hollowing joints are conducted with the neighbored carbon nanotubes. These network characteristics would receive much attention to the applications such as electrical conductiv-ity and even mass transport. Further work found that the as-obtained CNNW and CNNW/silver com-posites can both be applied as NH3 gas sensors. The solution-phase technique for the construction of CNNWs made the assembling networks possible without introducing physical and complicated meth-odologies, providing an alternative way for the next generation carbon nanotube assembly. Three-dimensional (3D) carbon nanotube networks (CNNW) have been constructed constructed by a simple solution route for the first time. The as-obtained networks consist of the ordered alignment of nanotubes cross-linked with a joint-angle of approximately 90o. Also, the joint points in the networks are very stable and the hollowing joints are conducted with the neighbored carbon nanotubes. These network characteristics would receive much attention to the applications such as electrical conductiv- ity and even mass transport. Further work found that the as -obtained CNNW and CNNW / silver com-posites can both be applied as NH3 gas sensors. The solution-phase technique for the construction of CNNWs made the assembling networks possible without introducing physical and complicated meth-odologies, providing an alternative way for the next generation carbon nanotube assembly.