Objective The internal jugular vein puncture catheter had some difficulties and challenges for obese patients.Whether positive end expiratory pressure and Trendelenburg position will increase the cross-sectional area of the right internal jugular vein in obese patients. Methods Forty patients were selected for perioperative period.Male-to-female ratio was 19:21;age ranged from 43 to 69 years. ASA wasⅠ-Ⅲ, and BMI was ≥ 30 kg/m2. After induction of general anesethesia and end intubation,the patients were placed in a supine position on a level bed with the head turning to the left 20°.The transverse diameter, anter-posterior diameter and the cross-sectional area of the right internal jugular vein were measured incrementally from the lowest to the highest with PEEP 0,5 and 10 cmH2O (1 cmH2O=0.098 kPa) and the head-down position angle of 20°. Ultrasound was used to measure and record the transverse diameter, anter-posterior diameter and the cross-sectional area of the right internal jugular vein at the level of the cricoid cartilage. Results All PEEP levels increased the transverse diameter, anter-posterior diameter and the cross-sectional area of the right internal jugular vein compared with the control: (1.38 ± 0.34) cm2vs. (0.73 ± 0.30), (0.97 ± 0.26) and (1.15 ± 0.30) cm2;(1.50 ± 0.30)cm vs.(1.00 ± 0.26),(1.18 ± 0.27)and(1.29 ± 0.26)cm;(1.01 ± 0.16)cm vs.(0.57 ± 0.16), (0.75 ± 0.18)and(0.84 ± 0.16)cm,P<0.05.Six patients were excluded because the blood pressure was below 90/60 mmHg (1 mmHg=0.133 kPa) after PEEP 10 mmHg was seted. Transverse diameter, anter-posterior diameter and the cross-sectional area of the right internal jugular vein was larger at the head-down position angle 20°compared with that at the PEEP levels.The largest cross-sectional area was (1.38 ± 0.34)cm2.Conclusions The use of positive end expiratory pressure and Trendelenburg position increases transverse diameter, anter-posterior diameter and the cross-sectional area of the right internal jugular vein in obese patients.Transverse diameter, anter-posterior diameter and the cross-sectional area of the right internal jugular vein is the largest at the head-down position angle 20°, then the PEEP 10 cmH2O.Airway pressure is the largest at the head-down position angle 20°.When we set the PEEP 10 cmH2O, some patients′ blood pressure is below 90/60 mmHg. AS for the airway pressure and hemodynamic instability, we recommend using PEEP 5 cmH2O to facilitate internal jugular venous cannulation in obese patients.