在网上找了一些办法，不太好用，还是该Extjs的样式来的最快。。。
将下列css加到Extjs所用页面。
.x-btn-default-large-mc {
padding-bottom:0px !important;
padding-left:0px !important;
padding-top:0px !important;
padding-right:0px !important;
}
.x-btn-default-large-tc {
height:0px !important;
}
.x-btn-default-large-tr {
padding-right:0px !important;
}
.x-btn-default-large-tl {
padding-left:0px !important;
}
.x-btn-default-large-bl {
padding-left:0px !important;
}
.x-btn-default-large-br {
padding-right:0px !important;
}
.x-btn-default-large-mr {
padding-right:0px !important;
}
.x-btn-default-large-ml {
padding-left:0px !important;
}
.x-btn-default-large-bc {
height:0px !important;
}
按钮属性scale: 'large'
Ext.define('HJ.view.Draw.DrawLineBtn', {
extend: 'Ext.Button',
alias: 'widget.DrawLineBtn',
id: 'DrawLineBtn',
//text:'折线',
iconCls: 'DrawLineBtn',
scale: 'large',
iconAlign: 'top',
height: 70,
width: 70
});
看效果。^^