尝试

var Default = $('div').css('font-family')
var sele = $('#editorFontN')

sele.val($('div').css('font-family'))

演示

sele.val($('div').css('font-family'));

演示

尝试这个

 var Default = $('div').css('font-family')
var sele = $('#editorFontN');
if ($('div').css('font-family') == "arial") {

    sele.prop('selectedIndex', 0);

} else if ($('div').css('font-family') == "alex_brushregular") {
    sele.prop('selectedIndex', 1);

} else if ($('div').css('font-family') == "quicksandregular") {

    sele.prop('selectedIndex', 2);

}

希望这有帮助，谢谢