Abstract: This paper firstly discussed how to establish simulated isosceles triangle in TOFD testing of T-joint to adapt to the default calculation program of depth location. Then,we introduced the modified calculation method between the measured depth and the actual depth, and verified the correctness of the above calculation method by calculating the error between the measured depth and the calculated value. Lastly, the rules of evaluating the defects, such as incomplete fusion in flange slab and web as well as defects in fillet weld on the T-joint were discussed through the analysis of the test results of T-joint.