According to the CAN FD protocol and the international standard ISO-11898, this paper adopts the hardware description language Verilog to design, and realizes the rate switching function of CAN FD controller. Through rate switching, the transmission rate of data frames in CAN FD can be increased from the traditional CAN rate to 12Mbps. The rate switching is realized by changing the period length of Tq, the minimum time unit in the component bit. The secondary sampling mechanism is applied in the data domain of the data frame to solve the data sampling problem of the transmitter. In addition, clock gating technology, resource sharing and traveling wave counter are used to reduce the power consumption.