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Gr.3 titanium tubes with two kinds of different oxygen content was designed, the thick-walled Gr.3 titanium tubes deforming cones were intercepted in accordance with determinate rule, then the micro-hardness on cross sections were tested, and the distribution curve of HV in the whole rolling duration was drawn. Comparing the microstructure at different positions of tubes rolled, the relation of HV variation and rolling process were investigated. Results show that the difference of HV on cross sections is large when the deformation rate is below 10%~20%, which is much more obvious in the case of lower oxygen content. The higher oxygen content is, the larger tendency of non-homogeneous of HV in radial direction of tubes becomes. As a result, the deformation rate should be greater than 35% and the entering amount should be small in the rolling process of thick-walled tubes; furthermore, the groove curve keeping smooth is beneficial to improve the quality of tubes.