Aim To observe the influence of haloperidol on QT interval and effects on L-type calcium channel mRNA expression.Methods By surface ECG technique and RT-PCR technique observe the influence of Various doses haloperidol to New Zealand rabbits ECG.And L-type calcium channel mRNA.Results Haloperidol elongated the QT interval.Haloperidol influence QT interval mainly happened after from 0 minutes to 120 minutes.360 minutes later,QT interval turned to normal standard.RT-PCR result display haloperidol obviously increase L-type calcium channel mRNA expression.Conclusion Haloperidol can prolong the QT interval.and it's mechanism concerned with increase L-type calcium channel mRNA expression.So,it can increase the risk of ventricular arrhythmias occur.