In this research, It has been carried out the development of a strength analytical method of a thin-walled steel square pipe (square hollow section/SHS) affected by the interaction of concentrated-compressive load and bending moment then it verified by experimental approach. the experimental approach was consisted of measuring a basic material property and the strength of the investigated SHS pipe. the basic material property identified parallel to rolling direction (0°) and perpendicular to rolling direction (90°). the analytical data obtained from cut-off strength method is generally scattered within the acceptable limits of ±, 20% and tends to be in unconservative region. the actual data measured from experiments shows that SHS beam with t = 0.6 mm and longitudinal axis parallel to the rolling direction of base material has higher strength compared to the one of the SHS beam with t= 0.6 mm and longitudinal axis perpendicular to the rolling direction, Meanwhile the SHS beam with t= 1.2 mm is tends to be equal. this means that the rolling direction of base material can be considered to be a parameter in the strength design of a thin-walled SHS beam.