Structural inspection is a series of processes that detect whether a submersible has undergone structural changes and damage after undergoing rigorous sea trials. The "Deep Sea Warrior" adopts the structural penetration coloring non-destructive testing method. First, professional flaw detection cleaning agents are used to clean the impurities and oil stains on the surface of the testing area, and then the flaw detection penetrant is sprayed. After standing for 10 to 15 minutes, the penetrant is removed and then the flaw detection imaging agent is sprayed. Then, the weld quality grade is evaluated based on the displayed crack size, quantity, length and other indicators.