Hydrogenated rosin Me ester (HRME) reaction kettle has been widely used in food, medicine, chem. industry. This article analyses the penetration crack failure of the temperature-measuring tube on the HRME reactor, which is made of 316L and installed in carbon steel head by welding. To find the root cause of the cracks, we conducted metallog., micro fracture, chem. composition, corrosion product anal., hardness measurement tests, and incorporated finite element modeling methods. Dendritic transgranular cracks and a small amount of intergranular cracks were observed in the fracture zone, and secondary bifurcation cracks appeared on the fracture sample. At the same time, the chloride ion content on the inner and outer surfaces of the cracks was 3.63 % and 2.93 %, resp. This indicates that the failure reason is transgranular stress corrosion and intergranular corrosion. In addition, there is significant thermal stress near the two welds of the temperature measuring tube.