In view of the deficiency found in the transmission speed and storage capacity of the external storage device of iOS mobile devices, a set of peripheral high-speed memory circuits suitable for iOS has been designed. By adopting the high-speed data transmission processing technology that meets USB3.1 standard requirement, which is also compatible with USB 2.0 standard, the transmission speed can be improved. Flash Raid management technology is to be applied for the integration of NAND and eMMC Flash chip data parallel transmission management, thus realizing the high-speed transmission and storage of dual-channel data with dual Flash chips reading and writing synchronously, as well as built-in multiple fault-tolerant mechanisms. The experimental results show that the redesigned high-speed storage circuit can adapt and expand the peripheral storage capacity, and improve the speed of speaking, reading and writing on the iOS terminal, with a speed as high as 25, 16 MB/s, thus achieving the purpose of high-speed transmission and storage of external storage in iOS mobile devices.