The constitutive equation and the secondary recrystallization maps, which reflect the flow stress characteristics and microstructure-deformation relationship of the material respectively, are the key data for the TC18 titanium alloy during the hot deformation. The hot compression deformation was taken on a Gleeble-3800 with the conditions that the deformation temperatures were 790℃~900℃, the strain rates were 0.01s-1~10s-1 and the strains were 0.1~0.5. By fitting the 6th polynomials of ε and α, n, Q, lnA in the Arrhenius formula respectively, TC18 titanium alloy’s constitutive equation of hot compression was established，the predicted values of flow stress of the hot compression are in a good agreement with the measured values; the secondary recrystallization maps of each strain rate were drawn by observing the microstructure and measuring α grains’ sizes.