The lighting system is a crucial component of manned submersibles, as it directly influences the operational efficiency and safety of the vehicle in complex underwater environments. This paper presents an innovative evaluation method for the lighting layout of manned submersibles, aiming to enhance their performance and reliability. Firstly, the study reviews current standards and practical application requirements for manned submersibles to establish clear objectives for the lighting design. Subsequently, a self-developed lamp is utilized to collect measurement data, which is then used to match an optical model and design a preliminary lighting layout scheme. To further validate and refine the lighting layout, DIALux software is employed to simulate the illumination of the target plane. Additionally, Lambert-Beer’s law and deep-sea water sample measurement data are incorporated to complete the equivalent conversion of illumination in deep-sea environments, ensuring the accuracy and reliability of the evaluation results. Based on the comprehensive analysis of the simulation and measurement data, an optimization strategy for the lighting layout is proposed. This strategy not only improves the lighting efficiency and uniformity but also enhances the safety and comfort of the manned submersible. Overall, this paper provides new insights and methodologies for the design and optimization of lighting systems in underwater equipment, contributing to the advancement of manned submersible technology.