Abstract: With the extensive application of low probability of intercept(LPI)radars, most of the interception of radar signals is in low signal noise ratio(SNR).The performance of the common parameter estimation algorithms of radar signals is inevitably corrupted in low SNR.To estimate the parameters of symmetrical triangle linear frequency modulation continuous wave(STLFMCW)signals in low SNR,a novel method is proposed based on the poly-phase filter bank and high-order cumulant. Firstly,the poly-phase filter bank split the signal into many narrow frequency bands rapidly.Secondly,the Gaussian noise can be suppressed by using the shorttime estimation of the third-order diagonal cumulant slices on each narrow frequency band.Then the estimation of the whole time-frequency matrixes can be obtained with envelope detection.Finally,the chirp rate,band width and period of STLFMCW signal can be estimated by radon transform of the time-frequency images.At the same time,the start-stop frequency can be estimated by extracting the frequency curves.Simulation results show that all parameters of the STLFMCW signals can be evaluated precisely when SNR is more than-12dB.