The influence of hydrogen contents on the tool wear has been mainly focused on the flank wear of the common tool,and the influence of hydrogen contents on the rake crater wear (main wear type) of the tool,particularly for the fine granular material tool,has been less investigated comprehensively.In this paper,for the purpose of researching the influence of hydrogen contents on tool wear,the titanium alloy Ti-6A1-4V is hydrogenated at 800 ℃ by thermohydrogen treatment technology and the turning experiments are carried out by applying umcoated WC-Co cemented carbide tool.The three-dimensional video microscope is used to take photos and measure tool wear.The results show that both of crater wear depth (KT) and average flank wear width (VB) firstly decreases and then increases with the increasing of hydrogen content.The maximum reducing amplitude of KT and VB is about 50％ and 55％,respectively.Under the given conditions,the optimum hydrogen content is 0.26％.It is considered that the reduction of cutting temperature is an important factor for improving tool wear after the Ti-6A1-4V alloy is properly hydrogenated.Furthermore,the reasons of hydrogen effect on the tool wear are chiefly attributed to comprehensive effect of hydrogen contents on microstructure,physical properties and dynamic mechanical properties of the Ti-6A1-4V alloy.The proposed research provides the basic data for evaluating the machinability of hydrogenation Ti-6A1-4V alloy,and promotes practical application of thermohydrogen treatment technology in titanium alloys.