1、普通模式，如图
QT QSS教程-QTabWidget_3c

/* 向在移动 */
QTabWidget::tab-bar {
    left:20px;
}

QTabBar::tab {
    background:qlineargradient(x1: 0, y1: 0, x2: 0, y2: 1,
                    stop: 0 #E1E1E1, stop: 0.4 #DDDDDD,
                                   stop: 0.5 #D8D8D8, stop: 1.0 #D3D3D3);
    border:2px solid #C4C4C3;
    border-bottom-color:red;
    border-top-left-radius:4px;
    border-top-right-radius:4px;
    min-width:8px;
    padding:2px;
}

/* 标签被选中时或鼠标悬浮时 */
QTabBar::tab:selected,QTabBar::tab:hover {
    background:qlineargradient(x1: 0, y1: 0, x2: 0, y2: 1,
                                stop: 0 #fafafa, stop: 0.4 #f4f4f4,
                                stop: 0.5 #e7e7e7, stop: 1.0 #fafafa);
}

/* 标签被选中时 */
QTabBar::tab:selected {
    border-color:#9B9B9B;
    border-bottom-color:#C2C7CB;
}

/* 标签未被选中时 */
QTabBar::tab:!selected {
    margin-top:2px;
}

2、被选中的标签，外框扩大，如图
QT QSS教程-QTabWidget_d3_02

QTabWidget::pane {
    border:4px solid #C3C7CB;
}

QTabWidget::tab-bar {
    left:20px;
}

/* 标签外形设置 */
QTabBar::tab {
    background:qlineargradient(x1: 0, y1: 0, x2: 0, y2: 1,
                                stop: 0 #E1E1E1, stop: 0.4 #DDDDDD,
                                stop: 0.5 #D8D8D8, stop: 1.0 #D3D3D3);
    border:2px solid #C4C4C3;
    border-bottom-color:#C2C7CB;
    border-top-left-radius:4px;
    border-top-right-radius:4px;
    min-width:50px;
    padding:2px;
}

/* 标签被选中时或鼠标悬浮时 */
QTabBar::tab:selected,QTabBar::tab:hover {
    background:qlineargradient(x1: 0, y1: 0, x2: 0, y2: 1,
                                stop: 0 #fafafa, stop: 0.4 #f4f4f4,
                                stop: 0.5 #e7e7e7, stop: 1.0 #fafafa);
}

/* 标签被选中时 */
QTabBar::tab:selected {
    border-color:#9B9B9B;
    border-bottom-color:#C2C7CB;
}

/* 标签未被选中时 */
QTabBar::tab:!selected {
    margin-top:2px;
}

/* 标签被选中时,外框向外扩大 */
QTabBar::tab:selected {
    margin-left:-4px;
    margin-right:-4px;
}

/* 最左边的标签被选中时,外框不变化 */
QTabBar::tab:first:selected {
    margin-left:0px;
}

/* 最右边的标签被选中时,外框不变化 */
QTabBar::tab:last:selected {
    margin-right:0;
}

3、标签居中，如图
QT QSS教程-QTabWidget_3c_03

/* 把显示界面向上移动 */
QTabWidget::pane {
    border-top:2px solid #C2C7CB;
    position:absolute;
    top:-10px;
}

/* 标签居中 */
QTabWidget::tab-bar {
    alignment:center;
}

QTabBar::tab {
    background:qlineargradient(x1: 0, y1: 0, x2: 0, y2: 1,
                                stop: 0 #E1E1E1, stop: 0.4 #DDDDDD,
                                stop: 0.5 #D8D8D8, stop: 1.0 #D3D3D3);
    border:2px solid #C4C4C3;
    border-bottom-color:#C2C7CB;
    border-top-left-radius:4px;
    border-top-right-radius:4px;
    min-width:20px;
    padding:2px;
}

QTabBar::tab:selected,QTabBar::tab:hover {
    background:qlineargradient(x1: 0, y1: 0, x2: 0, y2: 1,
                                stop: 0 #fafafa, stop: 0.4 #f4f4f4,
                                stop: 0.5 #e7e7e7, stop: 1.0 #fafafa);
}

QTabBar::tab:selected {
    border-color:#9B9B9B;
    border-bottom-color:#C2C7CB;
}

QT QSS教程-QTabWidget_d3_04