Objective To investigate the distribution and antimicrobial resistance of pathogenic bacteria isolated from infected patients in department of oncology, and provide scientific basis for rational selection of antimicrobial agents in clinical practice. Methods Antimicrobial resistance data of 102 570 bacterial strains from department of on- cology reported by China Antimicrobial Resistance Surveillance System (CARSS) from October 2020 to September 2021 were analyzed with WHONET 5.6. Results The main sources of specimens of patients from department of oncology were sputum (38.3%), urine (18.5%), and blood (12.2%). Among clinically isolated bacteria, the top 3 Gram-positive bacteria were Staphylococcus aureus (35.9%), Enterococcus faecalis (13.6%), and Enterococcus faecium (10.6%). Isolation rate of methicillin-resistant Staphylococcus aureus (MRSA) was 25.0%. Resistance rates of Enterococcus faecalis and Enterococcus faecium to vancomycin were 0.1% and 0.8%, respectively. The top 3 Gram-negative bacteria were Escherichia coli (30.6%), Klebsiella pneumoniae (21.7%), and Pseudomonas aeruginosa (12.0%). Resistance rate of Escherichia coli to third-generation cephalosporins cefotaxime and ceftria-xone exceeded 50%, resistance rate to carbapenems was about 1%. Resistance rate of Klebsiella pneumoniae to carba-penems was about 3%. The isolation rate of carbapenem-resistant Pseudomonas aeruginosa was about 6%. Conclusion Gram-negative bacteria are the major clinically isolated bacteria from tumor patients, resistance rate of which is not high. Rational use of antimicrobial agents should be strengthened in clinical practice, and monitoring on bacterial resistance should be conducted well.