Abstract: To address the critical demand for a highly stable observation environment in the study of laser-material interactions under vacuum conditions, this paper proposes a novel cubic vacuum chamber design based on the theory of non-circular cross-section pressure vessels. Conventional cylindrical chambers, while structurally efficient, often impose constraints on multi-axial optical access and system integration. This cubic design paradigm aims to better accommodate the geometric and functional requirements of advanced optical experimental setups. The structural design of the cubic vessel was conducted in strict compliance with the national pressure vessel code GB/T 150.3—2024. Its mechanical performance was rigorously validated through three-dimensional finite element analysis （FEA） under simulated external pressure loads. A key aspect of this simulation was the systematic investigation into the complex three-dimensional discontinuous stress transfer and concentration mechanisms prevalent in the chamber's corner regions. This detailed analysis provided critical insights into stress hotspots that are often neglected by simplified analytical models, forming the foundation for targeted structural enhancements. To ensure optical clarity and maintain vacuum integrity, an acrylic-metal composite observation window was designed and integrated. The parameters of this window assembly were optimized through a comprehensive approach that accounted for the long-term creep behavior of the acrylic viewport under vacuum and the deformation compatibility criterion at the critical metal-to-acrylic sealing interface. This dual consideration guarantees both a reliable, durable seal and minimal optical distortion throughout extended operational cycles. A parallel cost-benefit analysis of various wall-thickness schemes for the main chamber body was performed. This study revealed a pronounced nonlinear relationship between increasing wall thickness, material costs, manufacturing complexity （particularly for welding and machining non-standard thick sections）, and the marginal gains in safety factor, offering vital guidance for cost-effective design decisions. In response to the identified stress concentration at the corners, a localized reinforcement strategy is proposed, which is guided by fatigue assessment criteria rather than static strength alone, thereby ensuring enhanced durability against the cyclic loading from repeated pump-down and venting procedures. This holistic design has been successfully fabricated and implemented in a laser-driven vacuum experimental platform, demonstrating robust performance in practice. Consequently, this work establishes a comprehensive and transferable design framework for specialized optical observation equipment, effectively balancing the often-competing priorities of structural stability, economic feasibility, and precise functional compatibility.