Objective To investigate the effects of serum C-reactive protein （CRP） level and clinical symptoms on aggressive behavior in untreated first-episode schizophrenia patients. Methods A total of 164 untreated patients with first-episode schizophrenia in the department of outpatient and inpatient of Shandong Mental Health Center from January 2020 to November 2022 were selected as research subjects. The modified Overt Aggression Scale （MOAS） were applied to assess patients aggressive behavior. According to the results of MOAS， the patients were divided into the aggressive group （86 cases） and the non-aggressive group （78 cases）. The Positive and Negative Symptom Scale （PANSS） was used to evaluate the clinical symptoms of the patients. Binomial Logistic hierarchical regression analysis was used to analyze the influencing factors of aggressive behavior in untreated first-episode schizophrenia patients. Results The serum CPR level ［2.97 （2.46，3.47）mg/L vs 1.73 （1.36，2.10） mg/L］， total scores of PANSS ［（89.27±9.82） vs （83.47±8.04）］， positive factor scores ［33.90 （33.01， 34.79） vs 30.13 （29.28， 30.98）］， excitement factor scores ［14.12 （13.43， 14.80） vs 7.01 （6.41， 7.61）］， total scores of MOA ［12.85 （11.90，13.80） vs 2.28 （1.36， 3.20）］， verbal aggression scores ［1.28（1.15， 1.41） vs 0.38 （0.27， 0.50）］， aggression against property scores ［1.47 （1.32，1.61） vs 0.28 （0.15，0.41）］ and physical aggression scores ［2.01 （1.85， 2.17） vs 0.14 （0.01，0.27）］ of the aggressive group were all higher than those of the non-aggressive group， and the differences were statistically significant （P ＜ 0.01）. The negative factor scores ［24.63（23.64， 25.62） vs 28.15 （26.90， 29.40）］ and cognitive factor scores ［10.76 （10.24， 11.27） vs 11.60 （10.98， 12.23）］ of the aggressive group were lower than those of the non-aggressive group （P ＜ 0.05）. The results of binomial Logistic hierarchical regression analysis showed that long duration of disease was the independent protective factor of aggressive behavior in untreated first-episode schizophrenia patients （P＜ 0.05）. High score of excitement factor of PANSS and high serum CRP level were independent risk factors of aggressive behavior in untreated first-episode schizophrenia patients （P＜ 0.05）. Conclusions High score of excitement factor of PANSS and high serum CRP level are independent risk factors of aggressive behavior in untreated firstepisode schizophrenia patients. Patients with aggressive behavior have a shorter course of disease than patients without aggressive behavior， which may be due to the fact that aggressive behavior attracts more attention.