Based on the resource dependence theory, we explore the consequence of board capital on board decision quality as well as board supervision efficiency from the following two perspectives: human capital and social capital. The main results are as follows: Firstly, board human capital, such as average age, average tenure, average education level and constitute heterogeneity of age, tenure and education level, have no significant effect on board decision quality as well as board supervision efficiency. Secondly, Board meetings, one of board internal social capital, has no significant effect on board decision quality or board supervision efficiency. The proportion of internal directors has positive influence on both board decision quality and board supervision efficiency. Further, we test the mediation effect of board decision quality as well as board supervision efficiency and find that the direct effect of internal directors proportion on board decision quality is weakened due to the indirect effect of board supervision efficiency, while the direct effect of internal directors proportion on board supervision efficiency becomes insignificant due to the indirect effect of board decision quality. Lastly, interlocking directorate, one of board external social capital, is beneficial for improving board decision quality, while has no significant effect on board supervision efficiency. The results have important practical significance in improving board decision quality as well as board supervision efficiency.