Based on the demand asymmetric information in the dual-channel supply chain, which easily stimulates supply chain members’ fairness concern, the impact of the retailer’s fairness concern on the supply chain is studied, including the decisions and utilities of the members. Firstly, a threshold is defined to accurately determine the market size based on the retailer orders under considering the retailer’s fairness concern. Then, the retailer’s optimal order quantity and the manufacturer’s optimal direct selling quantity are obtained. It is found that the threshold is decreasing as fairness increases and it gradually becomes gentle. Numerical experiment results show that the retailer’s fairness concern benefits himself but hurts the manufacturer.