Based on a prototype of a Concrete Filled Steel Tubular(CFST) column (D=1.2m, t=24mm) used in a practical engineering, specimens length-diameter ratio of which is 3:1 are designed to conduct the uniaxial compression experiment according to three scales which are 1:2.4, 1:3.6 and 1:4.8. FE model is established to simulate the loading process by means of finite element software ABAQUS. The study shows that the bearing capacity of test is much higher than the value calculated according to codes. It’s about 7% higher than the design bearing capacity calculated according to code CECE28:90. The outer steel tubes of CFST columns used in engineering are generally processed by wrapping and welding. The welding zone is easily to yield firstly when the CFST columns are under uniaxial compression, which can change the compression bearing state of the cross section to bias compression. As a result, the bearing capacity of the CFST columns would decrease to some extend.