Abstract: Disassembled modular steel structures are characterized by high construction efficiency， economic and environmental benefits， flexibility， and reusability， and have widely used in scenarios such as temporary buildings， emergency response facilities， pandemic hospitals， and military engineering. However， their practical engineering applications face several challenges： 1） The contradiction between standardization and architectural diversity. 2） Unclear force transfer mechanisms exist in commonly used cold-formed open-section primary and secondary beams， with significant discrepancies between assumed and actual boundary conditions at connection joints. 3） Insufficient forms of joints between modular units and external hanging structures. To address these challenges， streamline modular specifications， and improve the mechanical properties， scalability， and application potential of disassembled modular steel structures in barrack construction， a new modular steel camp structure system has been developed based on traditional modular steel housing systems. This new system features efficient assembly and disassembly， flexible unit combinations， and enhanced floor insulation and compatibility with external hanging systems. The system comprises equilateral angle steel columns， equilateral corner fittings， locally reinforced cold-formed open-section primary and secondary beams， an insulated flooring system， an adjustable-height foundation， and external hanging structures. Lateral stiffness and vertical bearing capacity are key metrics for evaluating the mechanical properties of modular steel structures， and the new system introduces significant changes in these properties. Vertical and lateral loading tests were conducted to quantify the stress level at the connections between primary and secondary beams in the top and bottom frames， beam-end stresses， and external hanging structure stresses. Analysis revealed that under standard vertical loads， the overall deformation of the structure was well below standard requirements， demonstrating superior performance. Under lateral loads， the structure showed good lateral stiffness， with recommendations to control fabrication and installation tolerances for improved performance. The deformation characteristics of primary and secondary beams in the top and bottom frames and external structures were studied， complemented by experimental and finite element analysis to evaluate the stress behavior of external joints and foundation components. The results showed that simple hinge or rigid joint assumptions were insufficient to simulate the true mechanical responses of interfaces such as base-to-corner fittings， column-to-corner fittings， and corner-to-corner fittings in the modular steel structures. Refined simulations should account for interface separation characteristics. Additionally， extending secondary beams at least 40 mm into the web of top-frame primary beams could enhance the torsional resistance of primary beams and reduce stress levels at connection joints.