Abstract: Objective To investigate the effect of β3 adrenergic receptor (AR)agonist and antagonist on matrix metalloproteinases(MMP)-2 and MMP-9 in heart failure rat model and to study the relations betweenβ3AR and left ventricular remodeling. Methods Ten rats served as control group and 130 rats received isoproterenol to make heart failure model. Heart failure rats were randomly divided into agonist group(n=12), antagonist group(n=10), heart failure group(n=11). Agonist group and antagonist group received BRL37344 1.65μg/kg、SR59230A 50μg/kg through caudal vein for 10 min twice a week dividually. All below were measured at the 4th and 8th week: cardiac function, ratio of LV weight and body weigh(LVW/BW) and collagen volume fraction(CVF), expression of MMP-2 and MMP-9 proteins by the techniques of immuno-histochemistry; the expression levels of MMP-2 and MMP-9 mRNA in myocardium by reverse transcription-polymerase chain reaction (RT-PCR).Results Compared with control group，the cardiac function of heart failure group was aggravated while the cardiac function of agonist group was further aggravated; These change were significantly attenuated in antagonist group; In comparison with the control group, The expressions of MMP-2 and MMP-9 mRNA and proteins increased with time in heart failure models, and SR59230A treatment decreased the expression(all P＜0.01). Conclusions β3AR may play a role in left ventricular remodeling by the effect of MMP-2 and MMP-9.