He has published more than 160 journal papers and 40 books. He is the editor-in-chief of Journal of Combinatorial Optimization and book series on Network Theory and Applications. He is also in editorial boards of more than 15 journals. He is well-known for proving the Gilbert-Pollak conjecture on the Steiner ratio, the Derman-Leiberman-Ross conjecture on optimal consecutive 2-out-of-$n$ systems in reliability, and the global convergence of Rosen gradient projection method in nonlinear programming. In 1998, he received CSTS Prize from INFORMS (a merge of American Operations Research Society and Institute of Management Science) for research excellence in the interface between Operations Research and Computer Science. In 1996, he received the 2nd Class National Natural Science Prize in China. In 1993, he received the 1st Class Natural Science Prize from Chinese Academy of Sciences. In 1992, the proof of Gilbet-Pollak conjecture was selected by 1992 Year Book of Encyclopaedia, Britannica, as the first one among six outstanding achievements in mathematics in 1991.