The invention discloses a parking space sharing system and method based on a block chain. The system comprises an application layer, a server layer, a middleware layer and a data storage layer, wherein the server layer comprises data statistics, data processing and data query modules; the middleware layer comprises member management, Fabric SDK and chain code function modules; and the data storagelayer comprises relation and state databases. The method comprises the following steps: when a user searches for a shared parking space, the system firstly judges whether the user performs registration or not, then judges whether the parking space is being used or not and finally judges a credit point state of the user, and parking space reservation is carried out on the user meeting the condition; when the user arrives at the parking space, an order state of the user is judged, and a parking operation is carried out; and when the user finishes the use of the parking space, use evaluation issubmitted, the credit grades of the user and a parking space releaser are updated, and an order is completed. The system can realize the functions of releasing parking space sharing information and using the shared parking space, and has the advantages of being safe and reliable.