The　objective　of　this　study　was　to　assess　the　density　and　mechanical　properties　of　ancient　timber　members　based　on　the　active　infrared　thermography　(IRT).　Based　on　the　unsteady　heat　transfer　theory,　the　cooling　constant　(Ve)　was　proposed　and　the　relationship　between　Ve　and　density　as　well　as　the　mechanical　properties　of　timber　was　analyzed.　The　cooling　tests　were　conducted　on　50　small　clear　specimens　of　ancient　timber　members　to　obtain　the　Ve　and　the　cooling　law　of　specimens.　In　addition,　the　effect　of　heating　on　the　dynamic　modulus　of　elasticity　(Eus)　and　color　of　ancient　timber　members　was　investigated.　At　the　same　time,　static　mechanical　tests　and　density　measurement　test　were　carried　out　to　analyze　the　relationship　between　Ve　and　density　as　well　as　mechanical　properties.　The　results　indicated　that　there　was　unobservable　influence　on　Eus　and　color　parameters　(L*,　a*　and　b*)　of　specimens　with　its　heating　process　in　evaluation　of　the　density　and　mechanical　properties　based　on　active　IRT.　Meanwhile,　the　initial　excess　temperature　theta　0　and　initial　temperature　T0　had　no　influence　on　the　cooling　constant　Ve　as　well　as　the　relationship　between　tau　and　theta　in　the　cooling　process　of　specimens.　Moreover,　Ve　had　a　strong　negative　correlation　with　density,　modulus　of　elasticity　(MOE),　modulus　of　rigidity　(MOR)　and　compressive　strength　parallel　to　grain　(CSPG)　of　specimens　(R2　=　0.9768,　0.8493,　0.8714　and　0.8865).　In　addition,　the　validation　test　result　show　that　there　is　satisfactory　predictive　ability　for　density,　MOE,　MOR　and　CSPG　of　ancient　timber　members　based　on　the　prediction　models　established.