Abstract: Based on the improved straight chain plastic hinge model proposed by authors recently, the effects of two foam deformation modes on the compressive properties of foam-filled circular tubes were investigated. Considering the average crushing forces as the sum of average force of non-filled column, uniaxial resistance of foam, and the interaction between tube and foam, the analytical expressions of the optimal buckling half-wavelength and the average crushing force were obtained. The results show that the average crushing force under the foam deformation mode Ⅰ is a little higher than that of under the foam deformation mode Ⅱ , and the foam deformation modes greatly affect the optimal buckling half-wavelength. Compared with reference [14], the theoretical predictions of average crushing forces derived in this paper agree better with the experimental results.