Objective To investigate the change in serum hyaluronic acid (HA) level after the attack of spontaneous intracerebral hemorrhage (ICH) and its association with the prognosis of ICH patients.Methods A total of 284 patients with spontaneous ICH were enrolled in a prospective study,and their general information,medical history,clinical data,and imaging features were collected;95 healthy subjects matched for age and sex were enrolled as control group for comparison.The modified Rankin scale was used to evaluate the patients'conditions at 90 days after discharge,and according to this score,the patients were divided into good prognosis group and poor prognosis group.A statistical analysis was performed for these two groups.Results The ICH group had a significantly higher serum HA level than the control group (P<0.001).Among the 284 patients,211 had good prognosis and 73 had poor prognosis;the poor prognosis group had a significantly higher serum HA level than the good prognosis group (796.1±49.6 ng/ml vs 487.2±42.9 ng/ml,P<0.001).The HA level was positively correlated with the National Institutes of Health Stroke Scale score on admission (r²=0.372,P<0.001) and the modified Rankin Scale score at 90 days after treatment (r²=0.456,P<0.001).Conclusions Patients with acute spontaneous ICH have a significantly increase in HA level,and a high serum HA level on admission is a predictive factor for poor prognosis.