Objective To explore the shared genetic structure and causal relationship between respiratory diseases and obstructive sleep apnea (OSA) through comprehensive genetic analysis. Methods In this study, we utilized large-scale genome-wide association studies (GWAS) summary statistics and novel statistical genetic approaches. We incorporated genetic data related to respiratory diseases to align with OSA. We conducted a genome-wide cross-trait analysis to assess genetic correlation, identify shared loci, examine expression-trait associations, and infer causal relationships. Results We found positive genetic correlation between acute upper respiratory infections and OSA (rg=0.435, P=3.47×10?14), acute lower respiratory infections and OSA (rg=0.481, P=4.03×10?5), acute bronchitis and OSA (rg=0.453, P=7.00×10?4), pneumonia and OSA (rg=0.368, P=7.94×10?10), asthma and OSA (rg=0.364, P=2.73×10?19), and COPD and OSA (rg=0.300, P=1.10×10?10). We conducted a cross-trait meta-analysis to identify shared loci between respiratory diseases and OSA. Additionally, we employed summary-based Mendelian randomization (SMR) to predict causal genes associated with both respiratory diseases and OSA. Mendelian randomization (MR) supported the causal roles of pneumonia (IVW OR=1.15; 95%CI 1.02-1.30), asthma (IVW OR=1.05, 95%CI 1.01-1.08) in OSA, while not observe any significant association between other respiratory diseases and the risk of OSA. Conclusions An intrinsic link between respiratory diseases and OSA has been demonstrated. The genetic correlation and causal role of respiratory diseases in OSA emphasize the importance of considering respiratory health in the management of OSA.