We, in this study, investigate the attributes of relationship management variables in a supply chain. We select the industry material market where a small number of buyers select many suppliers. Our methodology framework for this study is composed of three stages. In the first stage, we use PLS(partial least square)) to select the input variable of DEA which is used in the second stage. We, in the second stage, apply DEA(CCR, BCC & FDH model) to select efficient and inefficient groups. In the last stage, we investigate the relations among relationship management variables as well as performance after classifying efficient and inefficient groups. We select conflict variable as the input variable of DEA and classify buyers and suppliers into ‘efficient group showing low conflict with parter company and high performance’ and ‘inefficient group showing high conflict and low performance’ to understand the effects of the variables such as dependency, relation norms, relation commitment, trust, power, and contract. We compare ‘characteristics of the relationship management variables of buyers and suppliers which manage conflict efficiently’ with ‘characteristics of the relationship management variables of buyers and suppliers which manage conflict inefficiently’to recheck many different findings which previous researches suggest regarding relations on a supply chain. Recently, contract between buyer and supplier becomes one of the important issues in our society. Thus, we analyze whether the exertion of power by buyer on supplier which is considered inferior to buyer is really effective in overall optimization in a supply chain. We find the characteristics of relationship management variables considering the level of trust rather than just referring that there are positive or negative effects of relationship management variables on the performance. We also find that the exertion of power by buyer on inferior supplier in terms of power does not result in positive effect on its own performance as well as overall performance of a supply chain. We, in the future research, include the consumer product market to generalize our findings in this research. We also try to find the relations among relationship management variables. We may test whether we can apply the sociological approaches for the conflict to the management of a supply chain and this sociological approaches result in the positive outcomes of a supply chain.