Abstract: After exposure to the ISO-834 Standard fire, the behavior of six concrete-filled steel tubular columns with rectangular sections has been experimentally investigated and the results are presented in this paper. It is found, within the scope of the test, the strength loss of the specimen without protection is significant. A model is developed in this paper for concrete-filled steel tubular columns with rectangular sections after exposure to the ISO-834 standard fire. The predicted load versus mid-span deflection relationship for the composite columns is in good agreement with test results. Influences of the parameters, such as steel ratio, steel and concrete strength, load eccentricity, slenderness ratio, length-to-width ratio of the section and sectional dimensions on the strength loss ratio are analyzed. A simplified model is developed for calculating the member capacity of concrete-filled steel tubular columns with rectangular sections after exposure to the ISO-834 standard fire.