RTC device driver on the PXA270 platform and Linux 2.6.31 kernel is designed in this paper. To design credible drivers, first, I2C bus and I2C driver framework are introduced. Then, all approach to the design of RTC driver based on ISL1208 is analyzed. And finally, RTC driver based on I2C is implemented and tested. This paper can provide some reference to RTC driver development on embedded systems.