A practical broadband analog fiber optic transmission system based on the laser diode direct modulation characteristic is reported. Its configuration and measured performance are described. The measured results indicate that -3 dB bandwidth of the system is 30 kHz～1.1 GHz, the dynamic range is no less than 40 dB within the nonlinearity of ±5% and the peak-to-peak amplitude of output noise is less than 5 mV. The system has many advantages, such as wide bandwidth, large dynamic range, low output noise and strong immunity to electromagnetic interference. It is suitable for the sub-nanosecond signal transmission in the complicated electromagnetic environment.