The relation between the maximum holding power ratio and the shear strength of the sea bed is discussed on the basis of experimental results of anchoring and sounding tests. Sounding tests have been performed with the device which is proposed in the present paper to measure the strength of the bed as the N -value. If the bed is in loose state as N <0.6, Danforth anchor is embedded deeply in it, and therefore its maximum holding power ratio becomes very large. On the contrary, Hall's anchor performs in the vicinity of the surface in any case and its maximum holding power ratio increases as the N-value. It should be noted that, when Hall's anchor moves on the bed, its holding power decreases suddenly because of its unstableness. In case of deep sea mooring, the anchor is dragged by wire or hawser with large scope angle. In order to prevent the anchor from lifting by large upward forces, a certain length of chain is commonly attached at the anchor shackle. In the present paper, behaviors of the chain are analyzed on the basis of experiments, and a chart is proposed for calculating the weight of chain necessary for satisfactory performances.