Objective To analyze the pathogenic characteristics and affecting factors for prognosis of patients with malignant hematological diseases complicated with blood stream infection (BSI). Methods Hospitalized patients with malignant hematological diseases complicated with BSI in the Department of Hematology in Affiliated Hospital of Zunyi Medical University between January 2016 and May 2022 were selected as the study subjects.Patients were divided into survival group and death group according to the treatment outcome within 30 days after BSI.Pathogenic characteristics and prognosis of patients were analyzed, risk factors for the prognosis of malignant hematological diseases complicated with BSI were analyzed by univariate and logistic regression. Results A total of 185 patients were included in study, the main underlying disease was acute leukemia (n=125, 67.6%).197 strains of pathogenic bacteria were isolated, 109 strains (55.3%) were Gram-negative bacteria, 55(27.9%) of which was Escherichia coli; 86 strains (43.7%) were Gram-positive bacteria, 24(12.2%) of which were Staphylococcus hominis; 2 strains were fungi (1.0%).28 strains (50.9%) of Escherichia coli and 2 strains (10.0%) of Klebsiella pneumoniae produced extended-spectrum β-lactamases.Isolation rates of methicillin-resistant coagulase negative staphylococcus, methicillin-resistant Staphylococcus epidermidis and methicillin-resistant Staphylococcus aureus were 70.8%, 71.4% and 36.4% respectively; univariate analysis showed that 30-day mortality was higher in patients with age ≥ 70 years, duration of agranulocytosis ≥ 7 days, irrational use of antimicrobial agents, combined with cardiac insufficiency, combined with acute renal insufficiency, septic shock and pulmonary infection, diffe-rences were all significant (all P < 0.05).Multivariate logistic regression analysis showed that duration of agranulocytosis ≥ 7 days (OR=3.306, 95%CI[1.224-8.927]), combined with cardiac insufficiency (OR=6.291, 95%CI[1.930-20.508]), combined with acute renal insufficiency (OR=8.419, 95%CI[2.198-32.241]), and septic shock (OR=22.150, 95%CI[3.639-134.806]) were all independent risk factors for 30-day mortality in patients with malignant hematological diseases complicated with BSI (all P < 0.05). Conclusion Among the most common pathogenic bacteria of malignant hematological diseases complicated with BSI, Escherichia coli is the main Gram-negative bacteria, and Staphylococcus hominis is the main Gram-positive bacteria.There are multiple risk factors affecting the prognosis of patients with malignant hematological diseases complicated with BSI.Shortening the duration of agranulocytosis, improving cardiac and renal function, and actively controlling septic shock are effective measures to reduce 30-day mortality in patients with malignant hematological diseases complicated with BSI.