In view of defects in the prior art, the present disclosure provides a controller in a high-speed serial peripheral interface (SPI) master mode, where clock signals are provided by a phase locked loop (PLL), and the entire controller includes: a low-speed clock domain and a high-speed clock domain, where the PLL provides two main clock signals by different clock frequency dividers, provides a low-speed clock signal to the low-speed clock domain, and provides a high-speed source clock signal to the high-speed clock domain. By such technical solutions in the present disclosure, functions of different clock domains are divided through asynchronization of a high-speed SPI controller, and the function of a high-speed SPI flash access is implemented, thereby saving a read/write time. Especially in an application scenario of an SPI flash boot, the controller can greatly optimize a startup time.