This paper presents the experimental study on the hysteretic behavior of unstiffened 300×300mm square box columns with tapered plates under a specified axial compressive load with the cyclic horizontal loads at the column top. The ratios of the thickness at the both ends of the tapered plates are 12/12, 9/12, 7.5/12 and 6/12, respectively, between the length of 900mm. Larger yield penetrations are obtained depending on the various action and resistant moment ratios along the specimens. Maximum horizontal loads may be lowered linearly with the ratios of the thickness to the uniform column.
