The invention provides an electric energy measuring method and device. The method includes the step of conducting low-pass filtering on electric signals so as to obtain analog signals, the step of conducting A/D sampling on the analog signals so as to obtain multiple discrete signals, the step of conducting improved generalized rapid S conversion on each discrete signal so as to obtain a first result matrix corresponding to the discrete signal, the step of conducting linear decomposition on each first result matrix through the linear characteristic of the improved generalized rapid S conversion so as to obtain a second result matrix corresponding to each frequency component of each discrete signal, the step of conducting inverse improved generalized rapid S conversion on each second result matrix according to the inverse nondestructive characteristic so as to obtain a reconstructed time domain signal corresponding to each frequency component of each discrete signal, and the step of obtaining the electric energy consumption value within the A/D sampling time interval so as to obtain the electric energy consumption value within the preset time. By means of the electric energy measuring method and device, the Gauss window shape can be adjusted according to the actual condition, and operation efficiency is improved.