Abstract: A new digital modulation recognition method based on instantaneous information is proposed for the application under the low signal-to-noise ratio(SNR).On the one hand,de-noising of instantaneous parameters is optimized by a wavelet filter,which can improve the recognition ability under the low SNR;on the other hand,the existing three feature parameters σ_ap,σ_aa and σ_fa,are used,and three new parameters Ra,Rp and Rf are proposed based on the existing feature parameters,which can simplify the process and improve the recognition ability.Simulation result shows that the algorithm is quite practical because the recognition ability probability is over 95.4% even if the SNR is low to 5 dB.