This work proposed a novel SAR characterization method based on an equivalent circuit model and the circuit’s frequency response analysis. Comparing to well recognized pulse energy method defined in NEMA MS 8, this method doesn’t need the flux loop fixed on transmit coil. Meanwhile, it can monitor SAR accurately. The Root Mean Square (RMS) error and maximum error of the novel method relative to the method in NEMA MS 8 are 4.96% and 9.47% respectively. This method could avoid design complexity of integrating the flux loop and has potential to be easily realized in most MRI scanners.