A severe disaster due to 921 earthquake occurred in the north wharf of Taichung harbor. The damages of wharf has been investigated and studied. This paper provide the detailed investigations which will be useful for the maintenance or construction for harbor engineering.After site investigation, it is found that the damages occurred in the north wharf include sand boiling, rupture, ground settlement, heaving and tilting of structures. The main reasons which caused the damages are the large intensity of shaking, soil liquefaction and leakage of sandfills behind the caissons.