Since low voltage power lines are affected by noise pollution, multi-path propagation and frequency selective fading in the process of signal transmission. It results in inaccuracy of timing synchronization, leak detection and misjudgment. A combined design scheme of timing synchronization and channel estimations proposed in this paper under the G3-PLC standard. Firstly, second-order cross-correlation with the local pilot is acquired to realize timing synchronization. Then the output of the correlator is used directly to achieve channel estimation. This design scheme improves the accuracy of timing synchronization and expands the range of SNR in normal work. Besides it simplifies the scheme of channel estimation. At last the hardware of the combined design scheme is accomplished. It uses FFT to calculated cross-correlation, which effectively reduces the computation and the amount of hardware resources. Meanwhile, compatible transmission mode of various CELENEC band is brought out.