A routing model for chord based on double identifier is proposed to address the problem that the routing table in Chord only covers half of the identifier space. The model assigns each node or key not only a clockwise identifier according to Chord but also a anticlockwise identifier in addition. So each node or key has double identifiers. Thus each node maintains two routing tables:clockwise routing table and anticlockwise routing table. Performance analysis and simulation experiments show that improved Chord routing model reduces the average lookup path length and gets higher efficiency.