Objective To explore the relevance of serum homocysteine (Hcy) level to erythrocyte and platelet parameters in patients with unstable angina pectoris (UAP). Methods Sixty patients with UAP were collected in Tongling Municipal Hospital from August 1st, 2012 to December 31st, 2015. Serum Hcy was measured by enzymatic cycling method. Erythrocyte parameters, such as red blood cell count (RBC), hemoglobin, mean corpuscular volume (MCV), coefficient of variation of red blood cell volume distribution width (RDW-CV), and platelet parameters, such as platelet count (PLT), platelet distribution width (PDW), mean platelet volume (MPV), platelet large cell ratio (P-LCR), were measured with blood cell counter. All patients were classified into UAP with hyperhomocystinemia (HHcy) group and UAP with normal Hcy group according to the level of Hcy. The data in two groups were analyzed and the relevance of serum Hcy level to erythrocyte and platelet parameters was evaluated. Results The differences in the levels of RBC, hemoglobin, MCV, PLT, PDW, MPV, P-LCR between the two groups were not statistically significant (P>0.05); while the levels of RDW-CV and the proportion of RDW-CV above the upper reference limit of patients in the UAP with HHcy group (13.81%±1.13%, 39.4%) were higher than those in the UAP with normal Hcy group (13.06%±0.97%, 4.8%), and the differences between the two groups were statistically significant (P<0.05). Correlation analysis showed that serum Hcy level of patients with UAP was significantly correlated with RDW-CV (r=0.380, P<0.01) and was not significantly correlated with other erythrocyte and platelet parameters (P>0.05). Conclusion The high level of Hcy affects red blood cell volume heterogeneity in patients with UAP, which may be one of the mechanisms of HHcy participating in the occurrence and development of UAP.