The invention discloses a dynamic allocation method of a user disk quota in a distributed storage system. The technical scheme comprises the following steps of: constructing and initiating a distributed storage system comprising a metadata server and storage servers; expanding the user local disk quota and storing user data if a storage access request received by a storage server aims to store data; deleting user data if the storage access request aims to delete data; setting the user local disk quota to be the occupation of the user local disk space, calculating the addition of the user local disk space and sending the addition to the metadata server; and calculating and sending the balance of a new user disk quota to all storage servers. The invention can dynamically expand or reduce the local storage space quotas of all the storage servers according to storage access requests, thereby not only suiting the dynamic change of the user data, but also improving the utilization ratio of the storage space.