Authors have developed a technique, called the cement-mixing and mechanical dehydration (CMD), as one of waste recycling and pollutant stabilization techniques. In order to investigate the strength improvement of the CMD in terms of physical properties of sample and cement mixing condition, unconfined compression test was performed for dredged clay at Kumamoto port, Kaolin clay, Masado (decomposed granite), Toyoura sand and blast-furnace slag treated by the CMD. Based on the result of unconfined compressive strength, principal component analysis was performed for the purpose of investigating the main factor to obtain high-strength cement-treated soil. Finally, the multiple linear regression function consisted of plastic limit, degree of saturation and water-cement ratio was proposed to estimate the unconfined compressive strength of soils treated by the CMD.