It is necessary to detect and monitor the distribution of mircophytobenthos (or algal mat) in tidal flats. KOMPSAT-2 will provide multi-spectral images with a spatial resolution of 4 m comparable with IKONOS. Using IKONOS and Landsat data, algal mat detection was tested in the Saemangeum area. Micro-benthic diatoms are abundant and a major primary product in the tidal flats. Fine grained upper tidal flats is considered to be the best conditions for microphythobenthos. A different type of microphytobenthos was found in coarse grained lower tidal flats. The newly reported microphytobenthos are algae and they began to exist after dike construction. A linear spectral unmixing (LSU) method was applied to the test data. The end-members were obtained by both spectral libraries built from field surveys and a remotely sensed image itself. End-members from spectral library were slightly more effective than those from image itself. A high resolution multi-spectral sensor in KOMPSAT-2 will provide useful data for long-term monitoring of microphytobenthos in tidal flats.