Blockchain, known as the engine of the fourth industrial revolution, is a universal framework of underlying technology. It is not only closely related to civil law, but also more likely to change the established rules of traditional private law. Blockchain simulates the real world trading process in a unique way, so it can be interpreted by the principles of civil law, and be expanded and applied. The smart contract technology built on it is believed to lead to deep transformation of financial and legal activities. By digitizing the content of the contract and deploying it on the blockchain, the execution of the contract can be carried out in a decentralized, trustless, and autonomous way. However, smart contract does not surpass the existing legal concept. Its essence is to add collateral function on the contract or the offer by technical means, so that the property interests directed by the contract can be transferred. For the current level of development, blockchain and smart contract technology are still in the early stage, most of the applications are concentrated in the stereotyped virtual scene, and there is still a certain distance from comprehensive popularization. Smart contracts also have multiple legal and technical bottlenecks, and there are a series of risks as well as challenges in such issues as coding loopholes, language transformation, reality interaction, transnational supervision and so on.