As an undergraduate student at University of Science and Technology of China in Hefei, Liu met Fang Lizhi, a pro-democracy activist. Then, at Peking University, Liu organized "Democracy Salons". Wang Dan later held a position there. Liu was a 28-year-old graduate when the 1989 demonstrations began. He organized the Beijing Students' Autonomous Federation and joined the movement's organizing body. As a result, he was sixth on a list of twenty-one activists whose arrests were ordered by the government. Liu went into hiding as a fugitive, but on 15 June 1989, Liu was arrested and charged with attempted subversion of the Communist Party of China. In 1991, he was convicted and sentenced to six years imprisonment at Qincheng Prison. After his release from prison in 1996, Liu continued to advocate for human rights in China and organized an underground democracy movement. After moving to the United States, Liu continued his studies at Columbia University in New York City. From there, he continued to support the Chinese democracy movement and in 2011, initiated further pro-democracy protests.
In 1996, Liu received a master's degree in computer science from Columbia University. He was invited to speak at the New York Academy of Sciences. Liu gained employment as a member of technical staff at the Mathematics of Networks and Systems Research Department at Bell Laboratories in Murray Hill, New Jersey. There he worked on Optical telecommunication network design and planning, routingalgorithms, optimization techniques, and economic models and strategy analysis. Liu's areas of research included: SPIDER, a design tool for fast-restoration in all-optical networks; VPNStar, a system for provisioning multi-service VPNs with Quality of service guarantees over Internet Protocol; in software design, a management system for Lambda Router in all-optical networks; and analysis of Internet pricing. During his days at Bell Laboratories, Liu introduced the A*Prune with K. G. Ramakrishnan, to describe a new class of Algorithm. This opened a new research direction in theoretical science. He found that A*Prune is comparable to the current best known-approximate algorithms for most randomly generated graphs. The algorithm constructs paths, starting at the source and going towards the destination. But, at each iteration, the algorithm is rid of all paths that are guaranteed to violate the constraints, thereby keeping only those partial paths that have the potential to be turned into feasible paths, from which the optimal paths are drawn. Liu also proposed a special class of Optical devices called SPIDER ; optical routers, dense wavelength division multiplexing systems, and cross-connects of unprecedented capacities. Liu and his colleagues are developing techniques for efficient and reliable optical network design, covering decentralized dedicated protection to shared path-based mesh restoration. Since 2011, Liu had been involved in a bitter divorce with his former wife, the judge presided the case had declared him mentally unstable, and appointed a custodian guardian to represent him against his wish; among Liu's accusations: his wife was a spy sent by Chinese Communist central committee to monitor him, and his ex-employer Morgan Stanley fired him to appease the Chinese government.
