Publisher Summary This chapter investigates the instability behavior of modular steel scaffolding systems. The structural analysis software NIDA is adopted to analyze the structural behavior of modular steel scaffolding systems. Second-order elastic analyses with geometrical nonlinearity are performed and all materials are assumed to be linear elastic. The analysis on of the elements of the modular systems is based on the self-equilibrium concept in which the internal moment balances the external moment at the midspan of the elements. The tangent stiffness matrix relates the incremental change in forces to a corresponding change in displacements and the tangent stiffness matrix can be formulated via a standard energy equation. The formulation of the analysis method is simple and the method follows a standard finite element procedure with only minimal amount of mathematical manipulation. The results show that the loading beam is considered to provide certain amount of positional restraints to the top of the steel scaffolding frames while the jacket base cannot provide fully fixed rotational restraints to the bottom of the frames.