Aim To explore the correlation between platelet morphology parameters and the severity of coronary artery disease in patients with acute coronary syndrome (ACS). Methods 121 ACS patients who were hospitalized in the Department of Cardiovascular Medicine of Second Affiliated Hospital of University of South China from January 2019 to October 2019 were selected, and 35 patients with normal results of selective coronary angiography during the same period were selected as the control group. Mean platelet volume (MPV), platelet distribution width (PDW), and platelet large cell ratio (PLCR) were used as platelet morphology parameters. All patients underwent coronary angiography and were divided into low score (1～40 points) group, medium score (41～80 points) group, and high score (81 points and above) group. The differences in platelet morphology parameters between each group were compared to identify risk factors for high Gensini scores. Results The MPV, PDW, PLCR, male proportion, creatine kinase isoenzyme (CK-MB), N-terminal-pro brain natriuretic peptide (NT-proBNP), uric acid (UA), and cardiac troponin I (cTnI) in the ACS group were significantly higher than those in the control group (P＜0.05). PDW, MPV and PLCR gradually increased in the control group and Gensini low, medium, and high score groups (P＜0.05). Pearson correlation analysis showed a positive correlation between PDW(r＝0.814,P＜0.05), MPV (r＝0.822, P＜0.05), PLCR (r＝0.802, P＜0.05) and Gensini score. Multiple Logistic regression analysis showed that PLCR can be a risk factor for high coronary Gensini score. Conclusion PLCR, PDW and MPV are positively correlated with the severity of coronary artery disease in patients with ACS, and have potential importance in evaluating the severity of coronary artery disease.