OBJECTIVE To explore the effects of posaconazole combined with proton pump inhibitors （PPI） on the blood concentration and the risk of invasive fungal disease （IFD） in patients with malignant hematological disorder. METHODS In accordance with the random number table method， 40 patients with malignant hematological disorders who were admitted to the hematology department of our hospital between December 2020 and December 2021 were chosen and divided into control group （20 cases） and observation group （20 cases）. The control group received Posaconazole oral suspension alone， while the observation group received Posaconazole oral suspension combined with PPI. The incidence of IFD， attainment rate of blood concentration， the time from the start of prophylaxis to IFD onset， the fatality associated with IFD， treatment of infected patients， and blood concentrations of posaconazole on 7th， 14th， 21st， and 28th day after posaconazole application were compared between 2 groups； the occurrence of adverse events during drug administration in the two groups was recorded. RESULTS The study was stopped because 2 patients in the observation group and 9 patients in the control group received hospital departures after taking posaconazole for fewer than 7 days. The incidence of IFD in the observation group was significantly higher than control group， and the attainment rate of blood concentration in the observation group was significantly lower than control group （P＜0.05）. There was no significant difference in the time from the start of prophylaxis to IFD onset， the fatality associated with IFD， treatment of infected patients and the incidence of adverse events （P＞ 0.05）. The blood concentration of posaconazole in the observation group was significantly lower than control group on 7th day of medication （P＜0.05）； there was no significant in blood concentration of posaconazole between 2 groups on the 14th day of medication （P＞0.05）. CONCLUSIONS Posaconazole combined with PPI can reduce the blood concentration of patients with malignant hematological disorders， increase the risk of IFD. Clinical practice should try to avoid the combination of the two or use them under the guidance of therapeutic drug monitoring.