Because the risk factors for oil and gas transmission pipeline have complexity and fuzziness, and the factor weights are difficult to distribute. Therefore the entropy weight method was used to determine the factor weights, and the fuzzy comprehensive was used to evaluate the risk. First of all, the basic principle of entropy weight method and steps of fuzzy comprehensive evaluation method were briefly described. Then a section of oil conveying pipeline in Beijing area as an example, the risk evaluation index system was established and the factors weights were determined by using the entropy weight method. Finally, the risk level was determined by using the fuzzy comprehensive evaluation method, and the result was consistent with the judgment made by field experts. And according to the evaluation results, the corresponding prevention measures were proposed, so as to verify the feasibility of the method.

For offshore pipeline in a multilevel, multivariable, multiple nonquantitative factors, the lack of effective means of quantitative assessment of the conditions, the establishment of a multilevel system of pipeline safety evaluation index, combining analytic hierarchy process to determine the corresponding layers of indicators weight through the use of multilevel gray theory, the pipeline system for safety assessment would affect the level of risk to quantify treatment, given the reliability of inservice pipeline quantify the results. Multilevel grey evaluation method for less data, small sample, incomplete information and lack of experience with the uncertainty calculation was simple, direct, scientific and practical, and could be used to service for the offshore pipeline safety assessment.