The new ternary complex of [Lu(POA)3phen]n (POA is phenoxy acetic acid, phen is 1,10 phenanthroine) was synthesized and crystal structure was determined by X ray diffraction.The crystal structure belongs to monoclinic system with space group P21/n.a=20.394(3)? ,b=8.513(1)? , c=20.708(3)? ,β =107.70(1)° ,V=3425.1(8)? 3,Z=4,Dc=1.568Mg· m- 3,μ (MoKα )=2.939mm- 1. Each Lu3+ ion is nine coodinated. Coordination polyhedron is a distorted trigonal prism. The carboxylate groups in the complex are bonded to the lutetium ion in the bridged bidentate and the bridged tridentate. Lutetium ions were linked by the bridged carboxylate groups, resulting in an infinite chain.