Abstract: This paper focuses on the system error correction of a millimeter-wave three-baseline InSAR. The system error correction scheme is presented, in order to achieve the signal amplitude and phase consistency between three channels. The effect of pulse compression, the impact of interference between channels, system phase stability, the slow time spectrum, amplitude and phase consistency level are analyzed. The unambiguous interferometric angle method based on three-baseline and the experiment on ground is presented. The effectiveness of the method proposed and the validity of the performance of millimeter-wave three-baseline InSAR are indicated by real data results.