Abstract: Objective: To establish the relationship between Feeding Intolerance (FI) of Early Enteral Nutrition (EEN) and Intra-Abdominal Pressure (IAP) in patients with Mechanical Ventilation (MV). Methods: Descriptive and observational study is carried out at the critical care unit in a 3A Grade Hospital in Beijing from April 2016 to January 2017. One hundred and ten patients with MV with an expected stay of more than 5 days and scheduled to receive EEN have been involved. Their IAP before the start of EEN and the first 3 days of EEN, and the incidences of FI during the first 3 days are all recorded. Results: The incidence of FI of the patients was 73.6%, and one of the most common symptoms is absent/abnormal bowel sounds (53.6%) and diarrhea (48.2%).Partial correlation analysis shows positive correlation between FI and IAP (P<0.05). The AUC under the ROC curve of baseline IAP and the average IAP during the first 3 days of EEN to predict FI are 0.81 (95% CI: 0.73-0.89) and 0.86 (95% CI: 0.79-0.93), and the best threshold are 9 mmHg and 11mmHg. Conclusion: Critically ill patients with MV face high incidence of FI. IAP and FI are related. The baseline IAP and the average of IAP during the first 3 days of EEN could predict the occurrence of FI.