An embodiment of the invention provides a data update method for a Key-Value storage system via distributed key values. Through replication of nodes requiring update, father nodes, ancestor nodes, and root nodes to a buffer layer of the Key-Value storage system, modification of key values and contents of the nodes requiring update, the father nodes, and the ancestor nodes, and modification of the contents of the root nodes, the nodes are made different from original nodes in the storage layer. The method is characterized in that, the nodes requiring update, the father nodes, and the ancestor nodes are first stored in the storage layer, and then the root nodes are stored in a key value pair system. Since the nodes requiring update in the buffer layer are stored in the storage layer prior to storage of the root nodes in the buffer layer in the storage layer, reading operation in the storage process of the nodes requiring update does not enable reading of the nodes requiring update, thereby preventing reading of dirty data. The invention also provides a corresponding method for reading index nodes and a server.