Fluidity　of　Ti-4Mo-3V-4Cr-0.5Fe-3.5Al-xO　alloy　with　different　contents　of　oxygen　addition　has　been　studied.　The　fluidity　of　alloy　displays　obviously　improvement　with　the　enhancement　of　oxygen　contents　up　to　0.6　wt%.The　influence　of　oxygen　on　the　microstructure　and　thermophysical　parameters　is　analyzed　and　discussed.　With　increase　of　the　oxygen　content,　the　changes　of　superheat,　solidification　interval　width,　viscosity,　and　density　exhibit　negative　effects　on　the　fluidity　of　alloy　melt.　However,　the　refined　grains,　enhanced　crystallization　latent　heat,　and　declined　thermal　conductivity　play　positive　effects　on　the　evolution　of　fluidity　for　alloy　melt.　And　positive　effects　dominate　the　evolution　of　fluidity.　Therefore,　the　addition　of　oxygen　can　improve　the　fluidity　of　Ti-4Mo-3V-4Cr-0.5Fe-3.5Al.