Decentralized finance (DeFi), powered by the underlying blockchain technology, aims to provide financial services without relying on a trusted third party. The importance of DeFi is reflected in its soaring trillions of market value as well as the on-ramping millions of active users in recent years. DeFi is so new yet revolutionary, thus studying how to build a sustainable decentralized financial system is necessary. This thesis provides research on three dimensions of sustainability, namely economic, social, and environmental, in order to create healthy, reliable, and thriving DeFi communities for this generation and generations to come.