The response speed of the white light emitting diodes(LED) affects the modulation bandwidth of the communication link and directly limits the data transmission rate of the white light communication system. In order to improve the communication rate when the modulation bandwidth is limited, a variable-period modulation white light communication system is designed. The data source is generated by the microcontroller at the transmitting end of the system, and the data is framed and modulated by a field programmable gate array (FPGA), and transmitted through the driving circuit and the LED light source. The FPGA at the receiving end of the system demodulates the digital signal output through the photodiode and the signal conditioning circuit. The experimental results show that the system effectively increases the data transmission rate compared to digital baseband modulation such as on-off keying, pulse position modulation, and differential pulse position modulation.