Incremental step strain-rate test in the temperature range of 700-800 oC and the strain rate range of 5′10-4–1′10-2 s-1 were conducted for investigation of high temperature deformation behavior of Ti-29Nb-13Ta-5Zr (Ti-29-13), as well as another typical β titanium alloy Ti-15V-3Cr-3Sn-3Al (Ti-15-3). Results show there exist discontinuous yielding phenomenon in both alloys and the subgrain behavior is different between them. The strain to failure of Ti-29-13 is lower than that of Ti-15-3. In the deformation of Ti-29-13, the stress exponent is near 3.3, which is almost constant, and the deformation activation energy is 152-161 kJ/mol; while in the deformation of Ti-15-3, the stress exponent at the temperatures higher than 730 oC is 2.3-2.5, and the deformation activation energy is 173-176 kJ/mol.