This book constitutes the thoroughly refereed post conference papers of the Second International Conference on Blockchain and Trustworthy Systems, Blocksys 2020, held in Dali, China*, in August 2020. The 42 full papers and the 11 short papers were carefully reviewed and selected from 100 submissions. The papers are organized in topical sections: theories and algorithms for blockchain, performance optimization of blockchain, blockchain security and privacy, blockchain and cloud computing, blockchain and internet of things, blockchain and mobile edge computing, blockchain and smart contracts, blockchain and data mining, blockchain services and applications, trustworthy system development. *The conference was held virtually due to the COVID-19 pandemic.