The TanDEM-X constellation is served by two X-band SAR satellites, which fly in close orbit formation acting as a large and flexible single-pass radar interferometer. This paper investigates the potentials for monitoring sea ice in the Bohai Sea with the unique constellation. Our results show that the coherence and interferometric phase of TanDEM-X data can be used to detect sea ice, and the radial velocity of sea ice can be measured with the along-track phase.