Background Decreased cardiorespiratory fitness (CRF) related to cardiopulmonary function increases the risk of cardiovascular disease in patients with end‐stage kidney disease. Thus, early detection of the cause of impaired cardiopulmonary function in patients undergoing peritoneal dialysis (PD) is of important clinical significance. Methods In this cross‐sectional study, symptom‐restricted cardiopulmonary exercise testing (CPET) was performed in 30 patients undergoing PD and in 23 age‐ and sex‐matched healthy control subjects. A fixed workload was added every minute until fatigue, and breath‐by‐breath respiratory gas was analysed with an automated gas analyzer at 10‐s intervals. Results The peak oxygen uptake (16.39 ± 0.83 vs. 25.77 ± 1.33 ml/kg/min p < 0.001) and the oxygen uptake at the anerobic threshold of patients undergoing PD (9.61 ± 0.34 vs. 14.55 ± 0.64 ml/kg/min; p < 0.001) were lower than in healthy control subjects, and both of these parameters correlated with body mass index and left atrial dimension. A steeper minute ventilation/carbon dioxide production slope (27.20 ± 0.68 vs. 24.29 ± 0.69；p < 0.01) and a lower end‐tidal carbon dioxide partial pressure (37.93 ± 0.54 vs. 41.27 ± 0.83 mmHg；p < 0.05) were observed in patients undergoing PD. The oxygen pulse and oxygen uptake efficiency slope was smaller in patients undergoing PD. The Maximum heart rate (126.07 ± 4.01 vs. 149.96 ± 5.29 bpm；p < 0.01) and 1‐min heart rate recovery (13.93 ± 1.52 vs. 24.39 ± 1.61 bpm；p < 0.01) were also lower in patients undergoing PD. Conclusion Subclinical cardiopulmonary dysfunction may exist in patients with PD, and a reduction in CRF in patients undergoing PD is affected by both central and peripheral functions. CPET has potential value in revealing the mechanism of impaired CRF and in discovering subclinical abnormalities in cardiopulmonary function.