With the continuous development of internet technology and increasing awareness of environmental protection among consumers, the dual-channel closed-loop supply chain management combining online direct sales channel and retail channel has received more and more attention, however, the existing research has neglected the service research, so this paper focuses on the service strategy in the dual-channel closed-loop supply chain. In this paper, we propose three service strategy models for dual-channel closed-loop supply chains, including when there is no service provision, after-sales service and recycling service provided by retailers and after-sales service provided by manufacturers and recycling service provided by retailers, compare and analyze the optimal decisions of supply chain members under the three service strategy models, discuss the role of service generated in dual-channel closed-loop supply chains, and propose a service cost-sharing strategy to achieve a Pareto improvement in the effectiveness of a dual-channel closed-loop supply chain. The study finds that service plays a positive role in the dual-channel closed-loop supply chain; the model of manufacturer providing after-sales service and retailer providing recycling service is the best service strategy choice in terms of economic and social benefits; the service cooperation mechanism of service cost sharing can achieve Pareto improvement of the supply chain within a reasonable range.