Data replication is a common method used to improve the performance of data access in distributed database systems. In this paper, we present an object replication algorithm in distributed database systems (ORAD). We optimize the created replicated data in distributed database systems by using activity functions of previous algorithms, changing them with new technical ways and applying ORAD algorithm for making decisions. We propose ORAD algorithm with using effective factors and observe its results in several valid situations. Our objective is to propose an optimum method that replies read and write requests with less cost in distributed database systems. Finally, we implement ORAD and ADRW algorithms in a PC based network system and demonstrate that ORAD algorithm is superior to ADRW algorithm in the field of average request servicing cost.