As a kind of electricity measuring instrument, the security of data storage in smart meters is quite important. With OIML R46 international recommendation published and more and more function used in smart meters, the method of large capacity data storage is needed. In this paper, the allocation of data storage is researched and the method of large capacity data storage in smart meters is presented, according to the characteristics of EEPROM and Flash and the importance of data storage in smart meter. The new method improves the efficiency and security of large capacity data storage, and extends the working life of storage. Meanwhile, it controls the cost of production effectively.