To further improve the ability that the Direct Sequence Spread Spectrum System restrains the narrowband interference, the paper realized adaptive threshold suppressing the narrowband interference basing on wavelet packet transformation. Through analyzing the power spread of the DS signal in wavelet packet transform, the thesis sets the adaptive threshold to orientate and reject the narrow-band interference. And the problem that the threshold is hard to settle is resolved. The adaptive threshold can quickly track and accurately locate the contaminate subsidiary-band, and be adaptive for the interference changing. Finally, the results of simulation demonstrate that the anti-jamming ability of the DSSS was further improved by the threshold algorithm.