This paper attempts to deal with a whole testing process of a floating open caisson in the strong tidal Qiantang Estuary. It offers an over-all description of the open caisson’s type selection, main principles regarding its structure design, building, floating, sinking, the joining of two open caissons and the operation of declination correction as well. In addition, the type of the open caisson, its self sinking, declination and swing in the test process are discussed in detail. All of these experiments might be quite useful in the building of a floating open caisson in similar strong tidal rivers. This paper attempts to deal with a whole testing process of a floating open caisson in the strong tidal Qiantang Estuary. It offers an over-all description of the open caisson’s type selection, main principles regarding its structure design, building, floating, sinking, the joining of two open caissons and the operation of declination correction as well. the addition of the type of the open caisson, its self sinking, declination and swing in the test process are discussed in detail. All of these experiments might be quite useful in the building of a floating open caisson in similar strong tidal rivers.