Objective: To explore the prognostic relationship between initial absolute lymphocyte count(ALC) of peripheral blood and primary immune thrombocytopenia (ITP) in children, in order to provide basis for judging the prognosis and treatment of ITP in children. Methods: Clinical data of 166 children with primary ITP in children admi-tted at the Affiliated Hospital of Guizhou Medical University from January 2014 to March 2018 were analyzed retrospectively, and they were followed up by clinic and telephone, the prognostic factors (gender, age, ethnicity, inducement, bleeding, initial ALC, platelet count and treatment) were statistically analyzed, and the relationship between ALC of peripheral blood and the prognosis of children with ITP was observed. Results: Of 166 children with ITP, 89 cases (53.6%) had remission within 3 months, 18 cases (10.8%) within 3-12 months, 20 cases (12.0%) within 1-4 years, a total of 39 cases (23.5%) were refractory (no remission in 1-10 years), the remission rate within 1 year was 64.5%, the total remission rate was 76.4%.ALC of remission cases was (4.58±2.87)×10⁹/L within 3 months, (4.47±2.04)×10⁹/L within 3-12 months, and (2.86±1.61)×10⁹/L within 1- 4 years.Thirty-nine cases (23.5%) were refractory(no remission in 1-10 years), ALC of them was (2.07±0.98)×10⁹/L, and there were significant differences among different groups (F= 12.06, P<0.01). Univariate analysis showed that age (F=27.28), pre-morbidity history of infection and vaccination history(χ²= 9.31), initial ALC (F=12.06) at initial diagnosis were related with the prognosis of children with ITP (all P<0.05). Multivariate analysis showed that the history of infection before onset, the history of vaccination(95%CI: 0.19 to 1.51, P<0.05)and initial ALC(95%CI: -0.64 to -0.23, P<0.001) at the time of initial diagnosis were independent factors affecting the prognosis of children with ITP.The receivers operating characteristic (ROC) was drawn with the development of chronic disease (course >12 months) as state variable and ALC as test variable.The area under curve(AUC) was 0.765(P<0.05), cut-off point was 3.925×10⁹/L, sensitivity was 0.542, and specificity was 0.966. Conclusions Initial ALC can be used as one of the prognosis index of ITP in children, and low ALC is the risk signal for chronic development of ITP in children.