Blockchains hold significant potential value in the implementation of trade-in policies, before and after adopting blockchain technology, four game models of dual-channel closed-loop supply chain were constructed considering two modes, where the manufacturer entrusts offline retailer to trade-in and directly trade-in through online channels and entrusts both online and offline retailers to trade-in simultaneously. The difference in motivations for manufacturer to adopt blockchains was explored. It shows that regardless of whether the blockchain is used or not, the manufacturer tends to trade-in directly through online channels. Meanwhile, the offline and online retailers tend to prefer the manufacturer to entrust them to trade-in. When consumers’ sensitivity to privacy information leakage is low and their sensitivity to information traceability levels is high, the manufacturer can achieve higher profits by adopting blockchains, and both the offline and online retailers can benefit from “free riding” at the same time.