Objective To study the correlation between the degree of anxious state in patients with unstable angina and the serum homocysteine (Hcy) level. Methods Totally 150 patients with unstable angina were included. All patients were tested by the self-assessment lists of anxiety (Self-rating Anxiety Scale, SAS), and divided into nonanxiety group and anxiety group. The serum Hcy level was detected. Results There were 68 patients with anxiety in the 150 patients with unstable angina, accounting for 45.3%. The age, SAS score, disease course and Hcy level in the anxiety group were significantly different from that in the patients without anxiety (P < 0.05). Prolonged disease course and increased Hcy level were the independent risk factors for anxiety of the patients with unstable angina (P < 0.05). The Hcy levels and proportion of HH in the mild group were statistically lower than those in the moderate and severe groups (P < 0.05). The Hcy level and proportion of hyperhomocysteinemia in the moderate group were significantly lower than those in the severe group (P < 0.05). Correlation analysis showed that Hcy level increased with the increase of SAS score (P < 0.05). Conclusions Hcy level is a risk factor for anxiety in the patients with unstable angina, and is correlated with the severity of anxiety. The unstable angina patients with elevated serum Hcy level should be closely watched for the emotional changes.