Abstract: In a high-speed and large-capacity storage system, the transmission channel is a real-time bidirectional link, and the microcontroller cannot sense the state of the storage device in real time, and the storage device needs to initiate data transmission actively. In response to this feature, a high-performance storage-oriented bidirectional SPI transmission interface is designed, and a set of extensible storage transmission protocols is defined to realize the transmission operations at the command level and the data level. The design is based on FPGA implementation. The comparison simulation results show that the transmission mechanism supports active transmission from the device to achieve true two-way SPI communication, and its transmission efficiency has obvious advantages over mainstream flash memory storage devices.