Objective:To evaluate the diagnostic value and safety of transbronchial lung biopsy and bronchoalveolar lavage (BAL) in pulmonary complications in patients with hematological tumors.Methods:A retrospective analysis was performed on 68 patients with hematological tumors combined with lung lesions from The University of Hong Kong-Shenzhen Hospital and The Third People's Hospital of Shenzhen from May 2016 to May 2022, including 37 males, 31 females, with a median age of 56 years (age range 21-90 years), among which 20 patients were >65 years old. Diagnostic fiberoptic bronchoscopy was performed with signs including fever, cough, hypoxemia, hemoptysis, unexplained dyspnea, and imaging changes. Patients with pulmonary masses were evaluated for transbronchial lung biopsy, including inner and outer leaf mass and high-density shadow of lung leaves, pathological and special staining of biopsy tissue (Grocott staining), BAL acquisition of bronchoalveolar lavage fluid (BALF) for microbiological smear/culture, cytomegalovirus, Pneumocystis jirovecii and Mycobacterium tuberculosis (TB) smear, TB DNA, TB and fungal culture. Etiological analysis of pulmonary complications and observation of the complications associated with fiberoptic bronchoscopy in patients with hematological tumors were conducted. Results:BALF test was performed in all patients after bronchoscopy, bronchoscopic lung tissue biopsy was performed in 46 cases. The total number of confirmed pathogenic infections was 40, including 12 cases of fungal infections, 9 cases of bacterial infections (2 cases each of E. faecalis and Pseudomonas aeruginosa, 1 case of Staphylococcus aureus, 1 case of Klebsiella pneumoniae, 1 case of E. coli, 1 case of coagulase-negative Staphylococcus, and 1 case of Streptococcus mitis), 9 cases of viral infection (5 cases of cytomegalovirus, 3 cases of parainfluenza virus type Ⅲ, and 1 case of respiratory syncytial virus), 4 confirmed cases of Pneumocystis jirovecii pneumonia, 3 cases of suspected mixed infection of Pneumocystis jirovecii and fungi, 1 case of Cryptococcus, 2 cases of suspected TB infection. No pathogenic organisms were found in 28 cases, including 6 cases of mechanized pneumonia, 6 cases associated with a history of hematological tumors, and 16 cases of other unidentified pathogens. All patients did not experience death or other serious complications caused by bronchoscopy complications. Conclusion:Pulmonary complications are common in patients with hematological tumors, and the application of transbronchial lung biopsy has good safety. Early examination of fiberoptic bronchoscopy can provide pathogenic diagnostic evidence of bacterial, fungal, Pneumocystis jirovecii and viral infections, thus improving the diagnostic rate.