A user data server system includes: a data storage node, which stores user data, registers the user data in a Distributed Hash Table (DHT) network by using a key, and receives and processes user data operation requests; a DHT index node, which creates and maintains DHT routing information according to a DHT algorithm and stores information of data storage nodes where user data is stored according to the key and searches for information of a data storage node where target user data is stored according to the key; a DHT super maintenance node, which manages and optimizes the DHT network; and a front end node capable of protocol processing and service processing, which obtains a key associated with a target user and obtains information of a data storage node where the target user data is stored by querying the DHT index node via the DHT network according to the key, and performs operations on the user data stored in the data storage node where the target user data is stored. With the technical solution provided by the present invention, a user data server is not centralized and is highly scalable and highly reliable with a high cost-effectiveness.