Objective:To investigate the effects of olanzapine versus risperidone on cognitive function, serum complement C3 and C4 levels and high sensitivity C-reactive protein (hs-CRP) level in patients with schizophrenia. Methods:Eighty patients with schizophrenia who received treatment in Lishui Second People's Hospital, China between September 2018 and September 2019 were included in this study. They were randomly assigned to receive treatment either with olanzapine (olanzapine group, n = 40) or risperidone (risperidone group, n = 40). Before and after treatment, the Positive and Negative Syndrome Scale (PANSS) score and the Wisconsin Card Sorting Test score were evaluated in each group. Before and after treatment, serum levels of dopamine, serotonin, norepinephrine, complement C3 and C4 and hs-CRP levels were compared between the olanzapine and risperidone groups. Results:Before treatment, there were no significant differences in PANSS and WCST scores between the two groups (both P > 0.05). After treatment, PANSS score, the number of perseverative errors and the number of random errors in each group were significantly decreased compared with before treatment [olanzapine group: (56.23 ± 9.37) points, (13.06 ± 6.26) points, (16.23 ± 6.35) points, t = 12.334, 5.885, 3.840, all P < 0.05; risperidone group: (55.98 ± 10.21) points, (13.97 ± 6.54) points, (16.31 ± 6.32) points, t = 12.044, 6.213, 3.321, all P < 0.05]. After treatment, the number of correct sorts and the number of categories in each group were significantly increased compared with before treatment [olanzapine group: (29.21 ± 2.24) points, (3.79 ± 1.12) points, t = 3.323, 2.087, both P < 0.05; risperidone group: (29.33 ± 2.35) points, (3.81 ± 1.15) points, t =2.750, 2.085, both P < 0.05]. After treatment, there were significant differences in these indexes between the two groups (all P > 0.05). Before treatment, there were no significant differences in serum levels of dopamine, serotonin and norepinephrine between the two groups (all P > 0.05). After treatment, serum levels of dopamine, serotonin and norepinephrine in each group were significantly decreased compared with before treatment [olanzapine group: (5.02 ± 0.13) μg/L, (66.24 ± 6.05) μg/L, (27.32 ± 4.05) μg/L, t = 67.800, 9.977, 5.082, all P < 0.05; risperidone group: (4.18 ± 0.12) μg/L, (63.12 ± 6.21) μg/L, (24.81 ± 4.13) μg/L, t = 99.761, 12.296, 6.882, all P < 0.05]. After treatment, there were significant differences in serum levels of dopamine, serotonin and norepinephrine between the two groups ( t = 30.029, 2.276, 6.882, all P < 0.05). Before treatment, there were no significant differences in complement C3 and C4 and hs-CRP levels between the two groups (all P > 0.05). After treatment, complement C3 and C4 and hs-CRP levels in each group were significantly increased compared with before treatment [olanzapine group: (1.12 ± 0.18) g/L, (0.24 ± 0.06) g/L, (1.09 ± 0.11) mg/L, t = 5.129, 4.049, 32.452, all P < 0.05; risperidone group: (1.13 ± 0.17) g/L, (0.25 ± 0.07) g/L, (1.10 ± 0.12) mg/L, t = 5.147, 5.164, 29.227, all P < 0.05]. After treatment, there were no significant differences in complement C3 and C4 and hs-CRP levels between the two groups ( t = 0.255, 0.686, 0.389, all P > 0.05). Conclusion:Olanzapine and risperidone have the same effects on improving the mental symptoms and cognitive function of patients with schizophrenia, but risperidone has more obvious effects on improving the body function than olanzapine.