Abstract: The three factors contributing to pipeline failures (corrosion, design and operation) are analysed and scored. As the most common destroyer of pipeline, corrosion mainly refers to internal and external corrosion. The internal corrosion has a risk score accounting for 30% of the total score for corrosion risks, depending upon the corrosiveness of the medium transported and the measures taken for corrosion control. The external corrosion, being a key factor in pipeline corrosion, relates to the following factors which are analysed and scored respectively: cathodic protection, coating quality, soil corrosion property, service age, buried metallic structure (if any), current interference, stress corrosion, etc. Original design has a strong bearing on risk. The design factor taken for the purpose of simphfing calculation will influence directly the risk condition due to its deviation. The following design factors are scored: the safety of steel pipe, the safety of system, fatigue, surge propability, hydraulic testing, and soil displacement. One important source of risk is incorrect operation. According to American statistics, about 62% of the failures result from incorrect operation, which usally occurs during design, construction, operation and maintenance. Improving the overall staff quality and enhancing third party supervision can minimize incorrect operation.