Recently, new development projects are being carried out with the soft ground located along the West coast and the South coast. As soft grounds have complex engineering properties that the load bearing capacity is low and high compressibility, it needs to solve this problems Prior to structures are constructed by the method of improvement of soft ground. The sand mat is usually being used for improvement of soft ground as a horizontal drain material and loading base. But, as the volume is enormous and an amount of demanded sand is increased, it is state of short in supply. This paper presents the feasibility study to use of precious slag ball instead of sand mat as the replacing material through the basic soil property tests, the medium of discharge capacity test and analysis of settlement character.