In this paper, a way of chaos secret communication based on parameter modulation is proposed. Our study shows that after parameter modulation some characters of the output of AOB chaos system are still kept, the time sequence of chaotic output still has continuous power spectrum, and looks like a random output. So information could be hid in the sequence. Computer simulation has also proved that secret communication with parameter modulation of AOB chaotic system is feasible. We have also studied influence factor of this system and their effects on secret communication.