Objective　To evaluate the changes of cardiac troponin I (cTnI) in diabetic patients undergoing lower limb surgery and the effect of pentazocine on the changes.　Methods　Ninety-three patients who were scheduled for orthopedic surgery in the lower extremity under intrathecal anesthesia were enrolled. They were divided into three groups (n=31): a non-diabetic patient group (group NDM), a diabetic group without treatment of pentazocine (group DM) and a diabetic group with treatment of pentazocine (group DM-P). Patients in group DM-P were intravenously infused with 0.5 mg/kg pentazocine 30 min before operation, while the same volume of normal saline was given in groups DM and NDM. Blood samples were collected 30 min before surgery and 24 h after operation. The serum concentrations of cTnI and calcitonin gene-related peptide (CGRP) were determined through enzyme-linked immunosorbent assay (ELISA). Intraoperative adverse cardiovascular events were recorded.　Results　Compared with group NDM, groups DM and DM-P showed remarkable increases in the concentration of serum cTnI 30 min before operation and 24 h after operation (P<0.05). Group DM presented marked higher levels of cTnI 24 h after operation than group DM-P (P<0.05). A remarkable increased level of cTnI in groups NDM and DM and a marked decreased level of cTnI in group DM-P were found 24 h after surgery, in comparison with those before surgery (P<0.05). Meanwhile, group NDM presented significantly higher levels of serum CGRP than groups DM and DM-P 30 min before operation (P<0.05). Compared with group DM, groups NDM and DM-P showed remarkable increased levels of CGRP 24 h after operation (P<0.05). The incidence of intraoperative adverse cardiovascular events was significantly increased in group DM (58.1%), compared with 22.6% in group NDM (P<0.05).　Conclusions　The level of serum cTnI is significantly increased in diabetic patients. Pentazocine can reduce the serum concentration of cTnI in diabetic patients 24 h after lower extremity surgery, which may be associated with the up-regulation of CGRP.