Objective To investigate the influence factors of olanzapine dose-adjusted plasma concentration in patients with schizophrenia. Methods A total of 544 schizophrenic impatients treated with olanzapine in Beijing Huilongguan Hospital from February to September 2020 were selected. Plasma concentrations of olanzapine were tested by high performance liquid chromatography-tandem mass spectrometry. The general information of patients was extracted from the medical record system， and the effects of age， gender， weight， combined medication and liver and kidney function on the dose-adjusted plasma concentration of olanzapine were analyzed statistically. Results The olanzapine dose-corrected plasma concentration of elderly group was significantly higher than that of young group［ （4.31±1.74） vs（ 5.11±1.88）ng（/ ml·mg·d）， t=4.263， P＜ 0.05］. The dose corrected plasma concentration of olanzapine in female patients was significantly higher than that in male patients［ （5.43±1.89） vs（ 4.02±1.57）ng（/ ml·mg·d）， t=9.148，P＜0.05］. The dose corrected plasma concentration of olanzapine in obese group was significantly lower than that in non-obese group［ （4.13±1.79） vs（ 4.55±1.80）ng（/ ml·mg·d）， t=2.095，P ＜ 0.05］. The olanzapine dose-corrected plasma concentrations corresponding to patients with olanzapine alone， olanzapine combined with risperidone， olanzapine combined with sodium valproate， and olanzapine combined with clozapine were（ 4.72±1.77）， （4.91±1.91），（ 3.52±1.06） and（ 4.39±2.23） ng（/ ml·mg·d） respectively. The differences among the four groups were statistically significant（ F=3.762， P=0.012）. Further pairwise comparison showed that the dose corrected plasma concentration of olanzapine was significantly lower in the combined valproate group than in the olanzapine group alone（ P＜0.05）. There was no significant effect of liver and kidney dysfunction on dose corrected plasma concentration of olanzapine（ P＞0.05）. Conclusions Age， gender， weight and combination of medication of schizophrenic patients all have effects on the dose-adjusted plasma concentration of olanzapine. When using olanzapine for treatment， clinicians should consider the combined effect of all factors and make a reasonable administration plan.