Nondestructive testing method for pipeline in complicated equipment

The invention relates to the field of detection, test and repair of a CDQ boiler device, and specifically, to a nondestructive testing method for an inner pipeline. The method comprises: selecting one point of a to-be-detected pipeline, enabling the point to peripherally couple to a magnetized magnetostrictive band, and leaving a certain gap between the head and tail of the magnetostrictive band; and making the magnetostrictive band externally surround an emission unit and a reception unit of an excited magnetic field signal, setting an echo signal threshold, and finding a defect point on the to-be-detected pipeline through judging an echo signal chart received by the reception unit of the excited magnetic field signal and combining the echo signal chart with the echo signal threshold. According to the method, defects hidden in the pipeline can be detected and found in advance, and pipeline state in heat exchangers and large boiler devices can be accurately judged rather than passive post-processing is carried out after accidents, such as leaking or pipeline burst, happen, thereby reducing cost of device repair and maintenance. Once the method is successfully applied and popularized, millions of maintenance cost is expected to be saved per year.