Large scale electric energy measurement has the problems of big scale of data, difficult of network scheduling and low measurement accuracy. In order to solve the above problems, this paper proposed the electric energy measurement mechanism based on the electromagnetic coupling system and the big data resonant cavity. Firstly, based on the opportunity coupling mechanism, the electromagnetic opportunity structure and the opportunity control parameters, the electric energy metering opportunity electromagnetic coupling system is constructed. The system has the ability to improve the working efficiency and the energy efficiency of the electromagnetic coupling system. Secondly, the influence of the power transmission network on the electric energy measurement is further eliminated by constructing a resonant cavity based on big data and using the near field opportunity. Finally, to the circuit quality factor of the big data resonant cavity could be obtained based on the combination between capacitance of the capacitor and the parallel diode and the opportunistic electromagnetic coupling system. The experimental results show that, compared with the current transformer ratio test instrument, the proposed algorithm has the advantages of high real-time, high precision and high efficiency etc.