Objective To investigate the oxygenation trend of critical patients with bacterial pneumonia under B-lineultrasound and PCT, so as to guide clinical diagnosis and treatment. Methods According to the method of random, 201 cases with pulmonary infection were selected from Guangxi Integrated Traditional Chinese and Western Medicine Hospital affiliated to Guangxi University of Traditional Chinese Medicine from February 2018 to August 2020. The lungs of each patient were examined by bedside ultrasound and their status was recorded. Meanwhile, the oxygen partial pressure, oxygenation index, calcitonin, age and gender were recored. Rank test of multiple random samples was used for the difference in oxygenation index distribution of each group, and pairwise comparison was conducted. 2 test was used for qualitative data. Results The incidence of respiratory failure was higher in the white Lung Group, B3 line group and B7 line group. The oxygenation index was mainly in the 0-100 mmHg and 101-200 mmHg segments. The oxygenation index of B3 line group was 101-200 mmHg. The oxygenation index of line B7 was mainly in 201-300 mmHg. In the normal lung ultrasound group, the oxygenation index was above JP2 and 300 mmHg. The results of rank test showed that the overall difference was statistically significant, and the difference between two groups was also statistically significant (all P＜0.05). In PCT＞10 ng/mL group, the oxygenation index was mainly in the range of 0100 mmHg and 101200 mmHg. The oxygenation index of PCT 210 ng/mL group was 101200 mmHg. The oxygenation index of PCT 0.5～1.99ng/mL group was mainly in 201～300 mmHg. The oxygenation index of ＜0.499 ng/mL group was more than 300 mmHg. The results of rank test showed that the overall difference was statistically significant, and the difference between two groups was also statistically significant (all P＜0.05). Conclusion The more B-line, the lower oxygenation index, the more prone to respiratory failure in critically ill patients with bacterial pneumonia. The higher the PCT, the lower the oxygenation index and the more prone to respiratory failure. The degree of lung B-line, PCT grade and oxygenation index range have corresponding significance. We should pay close attention to the B-line state of the lung, and evaluate the disease state by PCT examination, and pay attention to the oxygenation state in time, so as to guide the clinical diagnosis and treatment in time.