Objective To observe field potentials (FPs) and activation sequence at Langendorff perfused guinea pigs heart,SD rat cardiac tissue strips perfnsed by Tyrede's solution and cultured ventricular cardiomyocytes of suckling mice by microehtrode arrays (MEA) technique.Method FPs and activation sequence were recorded from perfnsed heart,cardiac tissue strips (5 mm×5 mm) and cultured ventricular cardiomyocytes by MEA.Results (1) FPs could be recorded in hearts perfused for 30 to 90 min with a heart rate 90-120 beats/mitt FP durations of beth ventricular and atrial tissue were (210±78) ms and (164±58) ms,respectively and atrial ventricular conduction time wag (320±150) ms.(2) The excitability of Tyrode's solution perfused tissue strips wag risible for more than 2 h,and FP durations of ventricular and atrial tissue strips were (115.80 ±11.61) ms and (83.71 ±6.48) ms,respectively.(3)Spontaneous beating frequency (150±100) beats/rain and FPs could be readily recorded in cardiomyocytes cultured between 2 to 72 hours.Conclusion MEAs is a sensitive,low noise and stable technique for observing local tissue action potential and activation sequence of whole heart,cardiac tissue strips and cultured cardiomyoeytes.