Aiming at the problems of hardware pre equalization technology and software pre-equalization technology based on finite impulse response(FIR) filter, a digital pre-emphasis software pre-equalization technology is proposed. The technology compensates the LED bandwidth according to the frequency response parameters of light-emitting diode(LED), and designs a direct-current biased optical orthogonal frequency division multiplexing(DOC-OFDM) underwater visible light communication system as an experimental test platform. The experimental results show that the modulation bandwidth of LED is increased from 7.8 MHz to 16 MHz by using digital pre-emphasis technology, and the implementation complexity of this technology is low, the flexibility is strong, and the signal spectrum after pre-equalization is more flat.