Medical pulmonary function testing equipment is a crucial tool for diagnosing respiratory diseases, but its interface design often suffers from information overload and complex layouts, leading to high cognitive load and poor user experience for healthcare professionals. This study employs electroencephalography (EEG) to explore the impact of different interface design factors, such as data visualization formats (single, dual, and triple combinations) and color schemes (color vs. grayscale), on cognitive performance and user experience. Using a 2 × 3 Oddball experimental paradigm, behavioral data (reaction time and accuracy) and EEG data (P200 and P300 components) were analyzed to evaluate the effects of interface design. Results indicate that complex visualization formats (e.g., graphs, tables, and scales) significantly increase P200 and P300 amplitudes, reflecting higher cognitive load. Color interfaces elicited significantly lower P300 amplitudes compared to grayscale, suggesting that color interfaces may enhance perceptual efficiency and decision-making. This study provides scientific evidence for optimizing pulmonary function testing equipment interfaces, recommending simplified visualization formats and color schemes to reduce cognitive load and improve user experience. The findings have significant theoretical and practical implications for the design of medical device interfaces.