Objective To investigate the correlation between small dense low-density lipoprotein cholesterol (sdLDL-C) and peri-operative myocardial injury (PMI) in patients with coronary heart disease (CHD) after percutaneous coronary intervention (PCI) and the predictive value of sdLDL-C for PMI. Methods A total of 141 CHD patients, 98 with angina and 43 with acute myocardial infarction, were retrospectively selected as the research subjects, who received elective PCI from January 2021 to June 2022, and 66 non-CHD individuals were selected during the same time. The clinical baseline data were collected, the distribution pattern of coronary lesions were recorded intraoperatively, and indexes such as the preoperative blood lipids and postoperative cardiac tropomom I (cTnI) were routinely tested. According to the postoperative cTnI value, the PCI patients were divided into the observation group with elevated cTnI level (n=86) and the control group with normal cTnI level (n=55). The two groups were compared for all the collected parameters, and the non-CHD group, the angina group and the acute myocardial infarction group were compared for sdLDL-C levels. SPSS 16.0 was used for statistical analysis. Data comparison between groups was performed using t-test orχ² test, depending on data type. Analysis of variance and trend testing were used for pairwise comparison among the three groups. The relationship between sdLDL-C and postoperative cTnI elevation was evaluated using binary logistic regression analysis. Results sdLDL-C, total cholesterol, low-density lipoprotein cholesterol (LDL-C), numbers of implanted stents, and total length of the stents in the observation group were significantly higher than those in the control group[(0.74±0.26) vs (0.56±0.27)mmol/L,(4.51±1.17) vs (3.90±1.04)mmol/L,(2.77±0.80) vs (2.25±0.73)mmol/L,(1.74±0.91) vs (1.33±0.62),(52.52±27.93) vs (36.92±19.41)mm,all P<0.05]. The logistic regression analysis showed that sdLDL-C (OR=14.798, 95%CI 1.112-196.904) and LDL-C (OR=3.074, 95%CI 1.138-8.302) were the independent risk factors of PMI (P<0.05). The area under ROC curve for sdLDL-C was 0.727 (95%CI 0.637-0.817; P<0.05) with the best cut-off point of 0.518 mmol/L, and a sensitivity of 86.0% and a specificity of 56.4% for the diagnosis of PMI, and the Youden index was 0.424. sdLDL-C was (0.541±0.144) mmol/L in the non-CHD group, (0.621±0.257) mmol/L in the angina group, and (0.776±0.289) mmol/L in the acute myocardial infarction group, with significant differences between groups (P<0.05) and a significant upward trend (P<0.05). Conclusion The preoperative high level of sdLDL-C is a risk factor of PMI after PCI in the CHD patients, and sdLDL-C has a positive correlation with the severity of the disease.