Ultra-high-speed, ultra-large-capacity and ultra-long-haul (3U) are the forever pursuit of optical communication. As a new mode of optical communication, 3U transmission can greatly promote next generation optical internet and broadband mobile communication network development and technological progress, therefore it has become the focus of international high-tech intellectual property competition ground. This paper introduces the scientific problems, key technologies and important achievements in 3U transmission research.During the study period (2010 – 2014), teams that have made contributions to the project are (in no particular order): Yang Qi’s team from State Key Laboratory of Optical Communication Technologies and Networks, Wuhan Research Institute of Posts and Telecommunications (undertaker of topic 1 “160_100 Gbit/s ultra-long-haul optical transmission theory and experimental verification”), Chi Nan’s team from Fudan University (undertaker of topic 3 “high spectral efficiency optical coding and modulation”), Yu Chongxiu and Xin Xiangjun’s team from Beijing University of Posts and Telecommunications (undertaker of topic 4 “high gain high flatness ultra-low noise parametric amplification”), Liu Deming and Cao Xiangdong’s team, Li Wei’s team, Fu Songnian’s team and Cui Sheng’s team from Huazhong University of Science and Technology (undertaker of topic 2 “multiwavelength self-related light source and correlation reception” and topic 5 “nonlinear suppression and high precision dispersion management”), Wang Xinmei and Wen Aijun’s team from Xidian University (participant of topic 3“high spectral efficiency optical coding and modulation”). Their efforts are all greatly appreciated.During the five years of this project, Prof. Zhou Bingkun (Academician of Chinese Academy of Sciences) has given us a lot of encouragement, support and help. The team members of this project would like to express their heartfelt thanks and wish Prof. Zhou good health and happy life.