To realize blind estimation of synchronization parameters of linearly digitally modulated signals in multipath fading channels and low signal-to-noise ratio (SNR), a joint algorithm for the estimation of carrier frequency offset, phase offset and symbol timing error based on cyclic cumulation is proposed. The mathematical relationships of cyclic cumulation and phase offset, symbol timing error are obtained through theoretical derivation. Based on this, the carrier frequency offset is roughly estimated firstly, then the quite precise estimation is obtained from the test of certain cycle frequency. Flinally, the phase offset and symbol timing error are estimated from the value of some certain cyclic cumulation. The algorithm do not rely on the color and distribution characteristics of the fading distortion or additive noise and is quite appropriate for complex condition that frequency offset, phase offset, time error and fading exist at the same time. Experimental results demonstrate the good performance of blind estimation of synchronization parameters in frequency selective fading channels under low SNR.