The study was purposed to evaluate synergistic effect of beta-lactam antibiotics in drug-induced hemolysis. The general information, including primary diseases, therapeutic drugs, infection pathogens in 6 patients with pulmonary infection and unknown reason anemia were integrated and analyzed. The leukocyte and reticulocyte counts, total bilirubin (TB), direct bilirubin (DB), fasting blood glucose (Glu in peripheral blood) were all determined by conventional method. At the same time, the erythrocyte direct antiglobulin test (DAT), complement fixation test (CFT), cell culture and smear examination were carried out. The antibodies in plasma were also detected by indirect antiglobulin test (IAT). The result showed that levels of WBC, TB, DB, Glu and reticulocyte in six patients treated with beta-lactam antibiotics were raised remarkably. DAT was strongly positive, but no RBC antibodies were detected in the plasma by IAT. The binding of red cells by monocytes or lymphocytes was great, and the hemolysis of red cells by alexin not appeared. After stopping above-mentioned beta-lactam antibiotic administration, patient's WBC, TB, DB, and Glu levels returned to normal values. Furthermore, DAT test result turned to negative. It is concluded that beta-lactam antibiotics lead to drug-induced hemolysis by non-specific adsorption of some proteins onto RBC surface, and their proteins may be considered as direct cause for this hemolysis.