Abstract: In oil & gas storage and transportation engineering, there are diversified design and construction schemes, from which the optimal one should be defined by comprehensive evaluation. Index weight plays an extremely important role in this evaluation. It can be used to identify the importance of different factors in the scheme and thereby determines the reliability and accuracy of the evaluation results. The methods for determining the weight vary depending on cases. Common weighting methods include subjective and objective weighting methods. In this paper, the current application of the weight in the oil & gas storage and transportation engineering and other fields is investigated and compared. Moreover, the future application of the weight in the oil/gas storage and transportation engineering is forecasted.