Abstract: This thesis is to obtain the basic form of the strength and stability capacity correlation equations of the concrete filled steel tubular structures under complex stress through the theoretical derivation.It is used the previous CFST equivalent truss model which had been obtained when establishing static equilibrium equations to do mechanical analysis under complex stress.It can be calculated the internal forces of each equivalent truss rod and then determined their yield failure pattern to get yield equation.It is also used the previous balance equation to do computings to offset the internal forces of steel and concrete, in order to obtain the bearing and stability capacity correlation equations.