To detect the carrier signal in the background of strong interference, a Duffing chaotic oscillator was applied to the triple-state pulse position modulation signal detection. The driving force f was adjusted in the detection process, which determined threshold fd of the system driving force. When the triple-state pulse signal was added in the system, which turned into a state of large-scale cycles from chaotic state, a periodic signal was detected in the input signals. If the system continued to be in the chaotic state, it indicated the input signal was the pure noise. Simulation results show that the method proposed can effectively detect a weak carrier signal when the signal to noise ratio is greater than -23 dB.