A model analyzing the effect of baseline oscillations on InSAR phase error is presented in this paper.By a baseline oscillations model

which includes horizontal oscillation and perpendicular oscillation

the models for SAR complex image of slave antenna and interferometric phase error are both deduced.Then effect of baseline oscillations on interferometric phase and quality of SAR image is analyzed.At last

a computer simulation on SRTM system is given.Through raw signal simulation of InSAR in time domain

raw signal for point target and extended scene targets are simulated.After imaging

complex image pairs and interferometric phase are obtained.The simulation results proved the validity of analysis.