Abstract: A new ORAM model is proposed in this paper. The blocks of the model are divided into different groups, data records and dummy records are stored in each group randomly. When the user accesses a record in the server each time, the other records in the same group are read into client or written into server. Every request of the users' only needs constant level access time according to a small amount of clint storage space and linear sever storage spece. The feasibility of the model is verified.