Abstract: The in-band radar cross section(RCS) of the microstrip antenna can be reduced efficiently by adding electromagnetic band gap(EBG) structure to the antenna, which makes targets hardly be identified. To recognize the targets with low RCS, the bi-static time domain scattering characteristics and the frequency domain RCS of the antenna is studied. The time domain sputtering characteristics of the microstrip antenna with EBG structure is studied by parallel FDTD algorithm. The formation mechanism of the time scattering waveform of the antenna is analyzed. Thereby, although the microstrip antenna with EBG has low RCS in frequency domain and exhibits stealth characteristic, the field amplitude of the time domain scattering waveform is very large at the beginning, and becomes lower after a period of time. It is called the time domain sputtering characteristic in this paper.