Abstract: β type Ti-xMo (x was mass fraction/%, 3-24) alloys were prepared by vacuum arc melting, and were treated by homogenization of 950 ℃×20 min and then were cooled to room temperature by water and furnace, respectively. The effect of Mo content and cooling method on point defect relaxation in the alloys was studied by internal friction test combined with phase and microstructure analysis. The results show that there were two Snoek-type relaxation peaks in the furnace-cooled and water-cooled Ti-xMo alloys. The relaxation peak changing characteristics with Mo content of furnace-cooled Ti-xMo alloys were similar to those of water-cooled alloys. The low-temperature peak height of Ti-xMo alloys under two cooling methods increased with the increase of Mo content during heating, but the peak temperature almost unchanged; the increase of peak height was attributed to the increase of β phase and interstitial oxygen atom content. Both the peak temperature and peak height of the high-temperature peak of water-cooled alloys increased with increasing Mo content, except for the water-cooled Ti-3Mo alloy; the increase in peak height and temperature was related to the enhancement of Mo and O interaction.