Welding is the process of joining materials in the manufacturing industry. To maintain the quality of welding results in accordance with established standards, it is necessary to inspect or inspect the product. To find out whether or not there are defects in the product before the next process is carried out, or before the product is marketed, an inspection is usually carried out using a non-destructive testing (NDT) method, namely testing materials without damaging the material being tested. Several types of non-destructive testing, namely, visual checking, penetrant test, radiographic test and magnetic particle test. This article discusses about the welding analysis of stringer tertiary screen at PT PAL Indonesia. To check whether there are defects in the welded joints in the stringer tertiary screen, a visual check and magnetic particle test have been carried out. Based on interpretation using ASME section IX, the test results show that there are several defects such as spatter on the base metal and wormholes which are unacceptable. The finding of this defect has been followed up with re-welding repairs as recommended. For spatter defects, repairs are carried out with the help of an air chipping hammer which functions to clean the spatter from the base metal, then for wormhole defects repairs are carried out by dismantling the weld and re-welding. The results of repeated visual checks and magnetic particle tests after repair showed that the defects had been successfully eliminated. Thus, the welding results on the stringer tertiary screen are acceptable.