Objective To observe the effect of Guanxinshuang Mixture（herbal mixture for coronary heart disease）on unstable angina pectoris and to explore its possible mechanism.Methods Fifty-six unstable angina pectoris patients were randomized into control group and treatment group

28 in each.The control group was given aspirin enteric-coated tablets

isosorbide mononitrate tablets and low molecular heparin

based on which

the treatment group was given Guanxinshuang Mixture as well.The treatment course was one month.Single symptom

angina pectoris and score of Seattle Angina Questionare were observed and the serum bioindicator was determined.Results The treatment group was significantly improved in relieving chest pain

chest fullness

shortness of breath

weakness and soreness in waist and knee

dizziness

and tinnitus;shortening the duration of angina pectoris

reducing the dose of nitroglycerin

and increasing SAQ score（P<0.05 or P<0.01）.After treatment

the hypersensitivity C reactive protein（hs-CRP）of the two groups was significantly lowered

and the lowering in the treatment group was more significant than in the control group（P<0.05）.In the control group

the matrix metalloproteinase-9（MMP-9）and the tissue inhibitor of metalloproteinase-1（TIMP-1）were not changed significantly

while in the treatment group

MMP-9 was reduced（P<0.05）but TIMP-1 was not changed significantly.Conclusion Guanxinshuang Mixture is effective in treating unstable angina pectoris.The mechanism is possibly owing to its anti-inflammation and stabilization of atherosclerotic plaques.