We　experimentally　investigated　the　influence　of　contact　contour　on　breakdown　characteristics　in　vacuum　under　uniform　field.　Four　vacuum　interrupters　were　used　and　their　contact　contours　were　designed　to　obtain　an　effective　area　(S(eff))　from　211　mm(2)　to　550　mm(2).　The　contact　parameters　were　contact　diameter　42.8　mm,　contact　gap　6　mm,　contact　thickness　16　mm　and　contact　material　CuCr50.　Basic　impulse　level　(BIL)　voltage　(1.2x50　mu　s)　was　applied.　Experimental　results　revealed　that　the　effective　area　S(eff)　had　a　significant　influence　on　the　conditioning　process.　The　larger　the　effective　area　was,　the　slower　the　conditioning　process　was.　When　the　breakdown　voltage　saturated,　the　breakdown　probability　distribution　followed　a　Weibull　distribution.　The　shape　parameter　that　represented　the　breakdown　voltage　scatter　was　constant,　independent　of　the　effective　area.　The　effective　area　(S(eff))　had　no　significant　influence　on　the　breakdown　voltage　under　a　uniform　field　in　vacuum.