Aiming at the problem of speechlike signal synchronization in encrypted communication across cellular mobile networks, a synchronous scheme combining time domain analysis with fast correlation method is proposed. On the basis of establishing the twostage synchronization model, the synchronous signal capture is implemented via the analysis of time domain characteristics of sinusoidal signal and the postcalibration algorithm. Furthermore, the accurate positioning of synchronous signals is achieved through the correlation calculation of Linear FM signals and the synchronous deviation compensation algorithm. Experimental results show that both of the error rate and leakage rate in the detection of synchronous signals are less than 001%, and the ratio of deviation that more than 5 samples is less than 003% in GSM and LTE network. The proposed scheme has good detection performance and low computational complexity.