Abstract: The consequent gravity at a pipeline failure, depending upon the hazard of leaking product and leaking surroundings, is expressed by the impact index of leakage, which is determined by mnedium risk and influence coefficient. The medium risk is divided into current risk and long-term risk, and the influence coefficient varies with medium and population in the area concerned. Leakage impact index can be evaluated with reference to the score of medium hazard and the influence coefficient recommended by relavent Arnerican institution. The higher the index, the higher its hazard. The relative risk score of pipeline, which can be determined by the damage index of the four causes of pipeline failure(third party damage, corrosion, design and operation) and leakage impact index, goes within 0 to 2000. The higher the score, the more safe the pipeline system, and the smaller the risk represented. By summing up the relative risk scores of different pipelines or the different sections of pipeline, we can determine the risk status of pipeline, as is of great value for long-term safe operation. The practice of evaluating a pipeline by means of risk scoring is advantageous to the cognition and application of risk evaluation in the field of pipeline industry.