Abstract: In a general way, optimization in oil and gas pipeline is based on annual conversion cost. And other factors are always ignored. Obviously, the results are not coincided with practice. Based on grey theory combined with the concepts of matter-element analysis, the grey matter-element decision analysis is proposed. This method systemically considers correlative technologic and economic indexes of the contrastive plans. The key points of this method lie in the buildup of composite grey element of all plans, the determination of multidimensional grey element of ideal plan and the composite grey element of associated coeffi-cient, and the calculation of correlativity. Correlative concepts and theory are expounded. And the applied method are showed by an example. This method is simple and the results are reliable. This method is fit for the optimization and decision-making of oil and gas pipelines and other engineering.