In the measurement of near field electromagnetic scattering characteristics, the transmitter′s high-power signal enters the receiver directly or after reflection, which is easy to cause the receiver block. After power amplifier, emission signal waveform changed and got a long tail, the tail and the target scattering echo signal enter into the receiver at the same time, the echo signal will be seriously affected by the trailing. Above problem will lead to the insufficient of receiver dynamic range and the measuring capability of the system is influenced. A method with time domain filtering and optimization design of antenna is proposed, which improves the receiver isolation of the near-field electromagnetic scattering characteristics of measuring and the low radar cross-section (RCS) measurement.