This paper considers a supply chain consisting of a manufacturer and a retailer. The manufacturer sells its products through the retailer and an online platform and adopts green technology in the blockchain era. The platform can operate with marketplace mode or reselling mode. The network effect is considered to reflect the power of the platform to enlarge the potential market size. In the decentralised supply chain, the online platform encroaches the offline demand despite the same retail price. The increase of the network coefficient improves the abatement level, and benefits the manufacturer and the platform but damages the retailer’s profit. For the supply chain coordination, the abatement level with reselling mode in the centralised supply chain is less than that in the decentralised supply chain if the network coefficient is high. Both marketplace mode and reselling mode can coordinate the supply chain if the network coefficient is low. Blockchain technology helps the products become greener and brings more profits for the manufacturer and the platform. And it induces supply chain coordination. Based on real data of a supply chain, its profit is increased by 3% after coordination.