Based on Michelson-Gires-Tournois interferometer (MGTI) structure of interleaver that both of reflecting mirrors were replaced by two mirror Gires-Tournois etalons (GTEs).The appropriate value of structural parameters such as GTE front surface mirror reflectance,the cavity length of GTE and interferometer arm length difference were chosen.Four groups of spectrums that the ratio of wide bandwidth port to narrow bandwidth port at 3 dB passband (bandwidth ratio) was 1.69,1.83,2.13 and 2.14 respectively,were obtained.They have high channel isolation,wide flat-top passband and different periods.The effects of these structural parameters upon output spectrum characteristics were systematically investigated.The numerical simulation results indicate that asymmetrical interleavers of different bandwidth ratios could be obtained using this MGTI.GTE front surface mirror reflectance influences the passband bandwidth and channel isolation.And the two kinds of influences are different.Choosing appropriate GTE cavity length and interferometer arm length difference,different frequency periods can be obtained.