Abstract: Duffing system is sensitive to specific signal and immune against the noise. This characteristic can be used to detect weak signal. For the fork problem of Duffing oscillator, intermittent chaos action represented by Duffing system in weak direct sequence spread spectrum (DSSS) signal detection is deduced through analyzing the Duffing system and Feigenbaum action. A new method based on intermittent chaotic action is proposed for weak DSSS signal detection. Finally, simulation experiment shows the validity of this method.