With the rapid development of the Internet, virtual communities are constantly emerging. While these communities provide innovative resources, there are also problems such as the low willingness of users to share and a lack of good incentive mechanisms. Blockchain can better solve these problems and promote community knowledge sharing. This paper constructs an online community knowledge sharing scheme based on Multi Chain, proposes the resource access and storage mode of “metadata & cloud storage”, designs the metadata information table in detail, and designs the overall framework of the knowledge sharing scheme and the key processes of some businesses. Based on the key process, the consensus mechanism of “Nominated Proof of Stake (NPOS)” is proposed to design the blockchain network, which realizes some functions of online community knowledge sharing. Through analysis and experiment, the scheme of this paper has good scientific rationality, safety and execution efficiency, and has good reference value for the development of other related projects.