The invention provides a multipath delay synchronous decision demodulation method based on short-time discrete Fourier transform. The method comprises the following steps: firstly receiving a carrier signal on a power line by a receiving end, and then filtering out of band noise through a band-pass filter; then performing sampling and quantization on the carrier signal after the band-pass filtering, and performing discretization on the signal; performing short-time discrete Fourier transform on a discrete sequence obtained by the discretization; performing approximating to obtain amplitudes at two carrier frequency; selecting the optimal branch; and performing demodulation decision by using the optimal branch information to accomplish the signal demodulation. The multipath delay synchronous decision demodulation method has the technical effects that the symbol synchronization can be quickly achieved, accurate signal demodulation is also achieved, the system is not affected by the initial phase of the carrier or the carrier frequency estimation error, robustness is high, and the implementation is easy. A simulation result shows that the performance of the method is close to the performance of coherent demodulation. A field operation result shows that the method has a high rate of communication results and is of a practical application value.