Objective:To investigate the clinical characteristics of patients who develop chronic critical illness (CCI) after sepsis.Methods:The survival patients with sepsis admitted to the department of critical medicine of Baoan Central Hospital of Shenzhen for the first time from April 2019 to October 2020 were enrolled. According to clinical outcomes, patients were divided into CCI group [intensive care unit (ICU) stay ≥14 days, with persistent organ dysfunction] and rapid recovery (RAP) group. The baseline characteristic on admission and clinical outcomes of patients in the two groups were collected and compared. Blood samples were collected to measure serum interleukins (IL-6, IL-10) levels and peripheral blood lymphocyte count (LYM) count were obtained from all patients after admission. The differences of above indexes on the 1st, 7th and 14th day in ICU between the two groups were compared, the 180 day cumulative survival rate of the two groups was observed.Results:① Twenty-two septic patients developed CCI and 28 patients with RAP were included. There were no significant differences in gender and infection site between the two groups. The age, acute physiology and chronic health evaluationⅡ(APACHEⅡ), sequential organ failure assessment (SOFA), proportion of septic shock, mechanical ventilation time, length of ICU stay, total length of hospital stay and proportion of secondary infection of CCI patients were higher than those in RAP group [age (years old): 61.0±13.8 vs. 50.3±13.9, proportion of patients aged ≥ 65 years old: 54.5% (12/22) vs. 25.0% (7/28), APACHEⅡscore: 20.5±4.4 vs. 14.4±4.3, SOFA score: 10 (7, 12) vs. 5 (3, 8), septic shock ratio: 40.9% (9/22) vs. 17.9% (5/28), time of mechanical ventilation (days): 18.5 (12.0, 28.0) vs. 5.0 (3.0, 7.0), length of ICU stay (days): 26 (18, 46) vs. 8 (6, 12), total length of hospital stay (days): 31 (26, 51) vs. 14 (12, 17), secondary infection ratio: 72.7% (16/22) vs. 7.1% (2/28), all P < 0.05]. ② The IL-6 levels of CCI group were higher than that of RAP group at all time points (ng/L: 176.86±103.54 vs. 113.32±71.34 on the 1st day, 84.72±46.06 vs. 54.98±26.61 on the 7th day, 44.28±20.20 vs. 17.76±4.70 on the 14th day, all P < 0.05). On the 1st and 7th day of admission, there were no significant differences in IL-10 and LYM levels between the two groups. On the 14th day of admission, IL-10 levels in CCI group were higher than that in RAP group (ng/L: 15.09±3.61 vs. 8.92±1.98, P < 0.05), while LYM was relatively lower [×10 9/L: 0.62 (0.43, 1.02) vs. 1.17 (0.93, 1.71), P < 0.05]. ③ The Log-Rank test results of Kaplan-Meier survival curve showed that the 180-day cumulative survival rate of CCI group was significantly lower than that of RAP group (63.6% vs. 96.4%, Log-Rank:χ 2 = 9.024, P = 0.007). Conclusions:Septic patients with advanced age, high APAHCEⅡscore and high SOFA score are prone to secondary CCI, resulting in long hospital stay, high secondary infection rate and poor prognosis. The occurrence of CCI may be related to the continuous expression of proinflammatory mediators and subsequent immunosuppression.