Abstract: To solve the problem that the signal to noise ratio(SNR) estimation error is large in the scattering multipath fading channel,a novel SNR estimation method based on spread spectrum signal was presented.Firstly,a troposcatter communication SNR estimation model was established to provide the scheme of SNR estimation and the data frame structure.Then,according to the characteristics that linearity frequency modulation(LFM) signal could separate multipath,a SNR estimation method based on spread spectrum signal was put forward,and the calculating formula of combined SNR was presented.Meanwhile an equivalent SNR calculation method based on specific received signal processing algorithm was proposed to represent the actual SNR in communication.The simulation results show that the method can provide accurate SNR estimation,the calculation method of equivalent SNR can educe more correct results and suit for a wider estimation range compared with other SNR estimation methods,can effectively carry out accurate SNR estimation of multipath channel.