Nowadays is the big data era. A large amount of data are generated which can be valuable for business, healthcare, transportation, etc. To promote the dissemination of the valuable data, researchers have been trying to design and develop data sharing platforms. However, the existing platforms fail to address at least one of the three issues: Trustworthiness, data heterogeneity, and authenticability. To this end, we propose TSAR, a fully-distributed Trustless data ShARing platform. In detail, we architect TSAR on Blockchain to remove the dependency on reliable third parties, which realizes the trustworthiness. Moreover, we propose a general data schema to represent raw data, which handles the problem of data heterogeneity. Finally, we record the data transaction as well as user-group information on Blockchain to achieve authenticability. To demonstrate the practicability and effectiveness of TSAR, we implement it in a minimal-viable-product fashion and evaluate the performance in terms of throughput and response time.