The cost structure of an enterprise will affect its ability to achieve operating profits. All kinds of operation and environment factors should be taken into account when enterprises making cost structure decisions. Among them, customer and supplier concentration is a key environmental factor for enterprises. However, the existing literature has little research on the potential relationship between supply chain concentration and corporate cost structure. This study examines the influence of supply chain concentration on the decision of enterprise cost structure. Using the cost data of the sample of China's manufacturing listed companies from 2012 to 2016, we found a positive correlation between the manufacturer's customer concentration and its cost elasticity. It also found that as the bargaining power of customers increased, the cost structure flexibility of companies with high customer concentration was weakened. At the same time, it is found that with the concentration of suppliers, the ratio of variable costs to fixed costs of downstream manufacturers is decreasing and the cost rigidity is strengthening. With the improvement of the bargaining power of the supplier industry, the negative relationship between the supplier concentration and the cost rigidity structure of downstream customers is weakened. Supply chain concentration and bargaining power are the decisive factors of the enterprise cost structure decisions