Abstract: Based on the tides of four ports in Yantai, Penglai, Longkou and Laizhou, the remote sensing images of Landsat series in 1984, 1995, 2005, 2010 and 2015 were selected and analyzed in Shandong Peninsula. The changes of tidal flat (including supratidal zone and intertidal zone) and coastline in the northern Shandong Peninsula in recent 30 years were analyzed. The results showed that the tidal flat area was reduced by 300.66 km² in the past 30 years, including intertidal area reduced 84.84 km², supratidal zone reduced 215.82 km², and the area was mainly concentrated in the southeastern part of Laizhou Bay. The length of the coastline was increasing and it increased by 103.68 km in 30 years with the growth rate 3.34 km/a. The typical increased areas were concentrated in Laizhou Taiping Bay, Longkou artificial island groups, Penglai Port and Yantai Port. It is found that the expansion of salt pan and aquaculture ponds, coastal erosion and sediment reduction were the main causes for tidal flat reduction. The expansions of coastal aquaculture pond and land reclamation were the major causes for coastline length increment.