Disclosed in embodiments of the present invention are a method for controlling brightness of a light source and a transmitting-end device. The method comprises: acquiring a target brightness value; determining the number of target-enabled sub-carriers required to achieve the target brightness value, and carrying designated data on the target-enabled sub-carriers so as to obtain an orthogonal frequency-division multiplexing (OFDM) frequency domain signal; determining the number p of OFDM+ symbols corresponding to the target brightness value and the number q of OFDM- symbols corresponding to the target brightness value, superimposing the p OFDM+ symbols on a low current of a PWM signal, and superimposing the q OFDM- symbols on a high current of the PWM signal, so as to obtain a driving current signal of a light source, wherein the driving current signal is used to control a current brightness value of the light source to be the target brightness value. The embodiments of the present invention can simplify an entire operation process of a receiving-end device, and improve demodulation efficiency.