Abstract: For a tubed concrete column, the tube gaps are usually arranged at the column ends to avoid the steel tube carrying loads directly. Two type square tubed steel reinforced concrete (TSRC) columns, i.e., a column with two gaps at the column ends and another column with an additional gap at the mid-height, are discussed in this paper. Experimental studies on the compression behavior of TSRC slender columns were conducted to investigate the effects of the width-to-thickness ratio of steel tube and the load eccentricity ratio. The failure modes, the ultimate strengths, and the load to tube stress curves were analyzed. The results indicated that the two type columns shown similar failure modes. The axial strength of column with additional gap at the mid-height was slightly higher than that of column with two gaps, while the eccentric strength of column exhibited opposite tendency. Parametric analysis were carried out based on the precise finite element (FE) models. Based on the test and FE results, the stiffness reduction coefficient to calculate the moment amplification effect was proposed by regression analysis, and the design method of square TSRC column with additional gap at the mid-height under eccentric compression was proposed.