Background Kawasaki disease (KD) is also known as multiple mucocutaneous lymph node syndrome of systemic vasculitis and is a leading cause of coronary artery lesions (CAL) in childhood. Intravenous immunoglobulin (IVIG) has been proven to effectively reduce the incidence of CAL, but the role and effect dose of aspirin in KD is still unclear. Moreover, overt bleeding and anemia are associated with the use of aspirin, and anemia is common in patients with KD. Thus, the aim of this study was conducted to compare the treatment efficacy, degree of anemia and inflammation, and changes in serum hepcidin in children who received a combination of high-dose aspirin and IVIG in the acute stage of KD, and those who received IVIG alone. Materials and Methods KD patients from two medical centers were retrospectively analyzed from 1999–2009. All patients were initially treated with a single dose of IVIG (2 g/kg) as the standard care of treatment. In group 1, high-dose aspirin was prescribed (> 30 mg/kg/day) until the fever subsided, and then low-dose aspirin (3–5 mg/kg/day) was prescribed until all the inflammation signs had resolved. In group 2, low-dose aspirin was prescribed without high-dose aspirin. Laboratory data were collected for analysis in both groups. Results A total of 851 KD patients (group 1, N = 305, group 2, N = 546) were enrolled in this study. There were no significant differences between group 1 and group 2 in terms of gender (p = 0.51), IVIG resistance rate (31/305 vs. 38/546, p = 0.07), CAL formation (52/305 vs. 84/546, p = 0.67), and duration of hospitalization (6.3 ± 0.2 vs. 6.7 ± 0.2 days, p = 0.13). There were also initially no significant differences in total white blood cell count, hemoglobin level, platelet count, and CRP before IVIG treatment between groups (all p>0.1). After IVIG treatment, group 1 had significantly lower levels of hemoglobin (p = 0.006) and higher CRP (p<0.001) as well as a smaller decrease in CRP level (p = 0.012). Furthermore, there was also a higher serum level of hepcidin and a delayed decrease in hepcidin level after receiving IVIG in group 1 (p = 0.04 and 0.02, respectively). Conclusions These results provide evidence demonstrating that high-dose aspirin in the acute phase of KD does not confer any benefit with regards to inflammation and it does not appear to improve treatment outcomes. Therefore, high-dose aspirin is unnecessary in acute phase KD.