This paper analyses the transaction characteristics and social capital governance mechanisms of the inter-firm transactions in industrial clusters and extends spot trading in the anonymous market from three dimensions: transaction domain, transaction rate, and transaction object. We establish transaction governance model based on social capital and analyze the main characteristics of enterprise transactions in industrial clusters: high frequency transaction is embedded in social network formed by inner transaction partners in industrial clusters. Based on these characteristics, a model of social capital governance mechanism on internal enterprise transactions in industrial cluster is established, and the main applicability conditions of the model are provided. The research results show that the existence of social capital leads to the effective governance of the internal transaction of the industrial clusters though constrained by the scale of industrial clusters and the level of information flow. When industrial clusters are small scaled and there are unobstructed channels for information communication, the traders have the motivation to implement collective punishment, but this mechanism is not applicable to the governance of transactions between the firms inside the clusters and firms outside.