The air-tightness test of ductile pipe needs to cover the cast iron pipe with soil. If there is leakage, the soil needs to be cleaned up and the concrete is broken. This will inevitably affect the progress of the project. In the common project implementation methods, generally, The airtightness inspection of ductile iron pipes is carried out in the following ways: the common methods of airtightness inspection include bubble method, smear method, chemical gas trace leak detection method, pressure change method, flow method, ultrasonic method and so on. The traditional leak detection methods mostly use the bubble method and the smear method. The bubble method is to immerse the workpiece in water, fill it with compressed air, and then collect the bubbles that leak out from it within a certain time to measure the amount of leakage. The smearing method is to smear a bubble-prone liquid such as soapy water on the surface of the workpiece with certain air pressure inside and observe the bubble generation to detect the size of the leakage. These two methods are simple to operate and can directly observe the leaking part and the leakage situation. However, because the leaking part and several leaks of the workpiece are not known in advance, it is difficult to collect all the bubbles, which affects the accuracy of the measurement; secondly, for the large and bulky, For parts with complex outer surfaces, bubbles are attached to the bottom and folds of the parts and are difficult to observe; after the test, the workpiece needs to be cleaned and dried, which cannot realize automatic and quantitative leak detection. Therefore, these two methods are incapable of meeting high-precision and high-efficiency production requirements. With the rapid development of computers, electronics, and sensor technology, the development of leak detection technology will usher in new development opportunities.