The　study　about　how　to　estimate　and　measure　the　complexity　of　traffic　flow　system　is　in　the　ascendant.　The　application　of　complexity　measure　methods　in　traffic　control　is　becoming　a　research　frontier.　In　this　paper,　the　simulation　tests　were　used　to　study　the　application　of　complexity　measure　in　traffic　control.　First,　the　improved　Lempel-Ziv　algorithm　was　introduced　to　scientifically　depict　the　complexity　of　a　traffic　flow　system.　Then,　the　follows　were　validated　by　simulation:　i)　whether　there　is　some　influence　of　traffic　control　on　traffic-flow　complexity　and　to　what　degree　the　influence　is　if　it　exists;　ii)　the　effect　of　complexity　as　a　control　index　on　the　output　of　traffic　control.　The　concludes　are　as　follows:　i)　the　complexity　of　a　traffic　flow　is　different　under　different　green　split,　which　indicates　that　the　complexity　of　traffic　flow　can　be　changed　by　traffic　control;　ii)　the　information　quantity　of　performance　function　is　enriched　by　the　accession　of　a　new　variable,　i.e.,　complexity,　which　shows　that　complexity　can　and　should　be　used　in　traffic　control.　©　2008　IEEE.