Abstract: 　Objective　To explore the clinical features and prognostic factors of sepsis in children without underlying diseases in pediatric intensive care unit (PICU). Methods　The clinical data of 110 children with sepsis who had no underlying diseases and were hospitalized in PICU from February 2014 to June 2016 were reviewed. According to the severity of sepsis, the children were divided into sepsis group, severe sepsis group, and septic shock group. According to the prognosis on 28 d after hospitalized in PICU, the children were divided into survival group and death group. The differences among different groups were compared. Results　In 110 children with sepsis and no underlying diseases (74 males and 36 females)  a median age was 0.42 years. Pulmonary infection is the main source of infection. The overall mortality rate was 14.55%. The mortality rates of sepsis, severe sepsis, and septic shock were 2.94%, 27.27%, and 35.48% respectively, and the difference was statistically significant (P<0.001).  The difference in procalcitonin (PCT), white blood cell (WBC), creatinine (Cr), activated partial thromboplastin time (APTT), international normalized ratio (INR), multiple organ dysfunction (MODS), the pediatric critical illness score (PCIS), pediatric multiple organ dysfunction score (P-MODS), mechanical ventilation within 6 h, the duration of mechanical ventilation and the prognosis on 28 days were statistically among those three groups (P all<0.05).  The difference in level of PCT, lactic acid (Lac), APTT, INR, MODS, PCIS, P-MODS, mechanical ventilation within 6 h, the duration of mechanical ventilation, PICU stay time, hospitalized time, the severity of sepsis were statistically different (P all<0.05) between survival group and death group. Logistic regression analysis showed that children with higher PCIS and longer hospitalized time had a better prognosis on 28 d, while those with longer mechanical ventilation had a poorer prognosis on 28 d (P<0.05). Conclusions　The levels of PCT, WBC, Cr, APTT, INR, MODS, PCIS, PCT, P-MODS, 6 h mechanical ventilation, and mechanical ventilation time were helpful in determining the severity of sepsis in children without underlying diseases hospitalized in PICU. PCIS, mechanical ventilation time, and hospitalized time affect prognosis.