Through the saturation magnetization for metal pipelines and the application of high-precision magnetic flux leakage inspection technology, the Magnetic Flux Leakage Pipeline Inspection Gauge detects the leakage magnetic field caused by corrosion defects and analyses the leakage magnetic field to assess the size and location of each corrosion defect quantitatively. The detector combines the information of the pipeline to process the early warning of pipeline leakage, estimation of lifetime and safety warning, which could be used for the security detection and maintenance. As a result, the corrosion degree and the lifetime of the pipeline could be determined, which provides the quantified information for maintenance or shutdown of the pipeline.