In　this　paper,　we　address　the　consensus-based　dynamic　boundary　observer　design,　where　the　freeway　traffic　network　modelled　by　the　linearized　Aw-Rascle-Zhang　traffic　flow　model　is　observed　by　a　network　of　sensors.　Inspired　by　the　consensus-based　static　boundary　observer　design　for　the　finite-dimensional　ordinary　differential　equation　systems,　we　further　propose　a　consensus-based　dynamic　boundary　observer　and　directly　analyze　the　detectability　for　the　infinite　dimensional　traffic　system　by　means　of　Lyapunov　techniques.　The　sufficient　conditions　for　the　distributed　consensus-based　boundary　observer　in　terms　of　matrix　inequalities　are　also　provided.　Finally,　the　performance　of　the　proposed　approach　is　tested　by　some　numerical　simulations.　©　2020　Technical　Committee　on　Control　Theory,　Chinese　Association　of　Automation.