During the process of interrupted cutting, milling insert suffers from periodic thermal shock. The bad temperature field caused by cutting heat is the direct reason for tool failure. In order to get more accurate temperature field distribution of milling insert, the experimental research on temperature field is carried on with the FLIR infrared thermal imager. This paper takes hard cutting material 3Cr1Mo1/4V as example. Through the contrast experiments, the temperature field distribution of tool-chip contact area is gained at the moment of milling insert going into or out from the workpiece, and also the difference of failure modes among different milling inserts is revealed. The experimental analysis results show that more accurate distribution of temperature field will be obtained when we apply the infrared thermal imager to observe temperature field during interrupted cutting process. Optimization design for groove of milling insert also can be based on those results.