Objective To analyze the clinical effect of low glycemic index diet combined with antipsychotics in the treatment of schizophrenia. Methods From September 2019 to August 2020， 80 schizophrenic patients who were hospitalized in Shanghai Huangpu Mental Health Center were selected as the research objects. They were divided into control group and observation group with 40 cases in each group by random number table method. The observation group was given low glycemic index diet therapy on the basis of the original antipsychotic drug treatment， while the control group was given ordinary ward diet on the basis of the original antipsychotic drug treatment. The therapeutic effects of the two groups were compared. Results After dietary treatment， the total scores of the Positive and negative symptom scale（ PANSS） and the scores of positive symptom factors， negative symptom factors and general psychopathological symptom factors of the observation group showed a downward trend. After repeated measures analysis of variance， the PANSS total score showed that the differences in the main effects， time main effects， time and group interaction effects were statistically significant（ F1=6.783，P1=0.011；F2=41.378，P2＜0.001；F3=41.378，P3＜0.001）； positive symptom factor scores show that the main effect of time and the difference between time and group interaction are statistically significant （F1=10.302，P1＜0.001；F2=6.483， P3＜0.001）， the main effect difference between groups No statistical significance （F=0.384， P=0.537）； negative symptom factor scores showed that the differences in the main effects and the interaction effects of time and grouping between groups were statistically significan（t F1=4.655， P1=0.035；F2=37.087， P3＜0.001）， the main effect of time was not statistically significant（ F=2.594， P=0.054）； general psychopathological symptom factors showed that the main effect of time and the interaction effect between time and group were statistically significant（ F1=36.177，P1＜0.001； F2=37.087， P2＜0.001）， the main effect difference between the groups was not statistically significant（ F=3.670， P=0.071）. Starting from the 8th weekend， the differences between the groups of PANSS total score， negative symptom factor score and general psychopathological symptom factor score were statistically significant. At the end of the 8th week， they were（ t1=3.507， P1=0.001； t2=2.126，P2=0.037；t3=2.839，P3=0.006）， respectively（ t1=4.337，P1=0.001；t2=3.201，P2=0.002；t3=3.000， P3=0.004）. Starting from the 4th weekend， the PANSS total scores， positive symptom factor scores and general psychopathological symptom factor scores of the observation group were statistically significant compared with those before treatment. At the 4th weekend， they were（ t1=7.481；t2=3.616；t3=5.430，P ＜ 0.05）， at the 8th weekend（ t1=7.649；t2=4.572；t3=7.531，P＜0.05）， at the 12th weekend（ t1=7.564；t2=4.869； t3=7.622，P＜0.05）. During the study， there were no serious adverse reactions such as hypoglycemia， and no abnormalities in liver and kidney function， and the safety was good. Conclusions The low glycemic index diet may increase the effect of antipsychotic drugs in improving mental symptoms， and may have a certain effect on the further improvement of negative and positive symptoms. It may be an effective treatment plan with good safety.