使用CSS制作小三角形实际就是通过控制块元素的边框来实现的。
例如：
<style>
.triangle-up {
width: 0
height: 0
border-left: 50px solid transparent
border-right: 50px solid transparent
border-bottom: 100px solid red
}
.triangle-down {
width: 0
height: 0
border-left: 50px solid transparent
border-right: 50px solid transparent
border-top: 100px solid red
}
.triangle-left {
width: 0
height: 0
border-top: 50px solid transparent
border-right: 100px solid red
border-bottom: 50px solid transparent
}
.triangle-right {
width: 0
height: 0
border-top: 50px solid transparent
border-left: 100px solid red
border-bottom: 50px solid transparent
}
</style>
<div class='triangle-down'></div> <!--向下三角形-->
<div class='triangle-up'></div> <!--向上三角形-->
<div class='triangle-left'></div> <!--向左三角形-->
<div class='triangle-right'></div> <!--向右三角形-->
原理就是设置块元素的三条边透明掉（tranparent）
你好，我这里用CSS实现了三种带边框三角，效果分别如图：
实例代码如下，根据你个人的情况调整代码吧：
<!DOCTYPE html><html lang="en">
<head>
<meta charset="UTF-8">
<title>Arrow</title>
</head>
<body>
<style>
/* scale */
.arrow,
.arrow:after{
position: relative
display: inline-block
width: 0
height: 0
border-top: 0
border-left: 30px dotted transparent
border-right: 30px dotted transparent
border-bottom: 30px dashed #000
}
.arrow:after {
position: absolute
top: 0
content: ''
transform: translateX(-50%) scale(.8)
border-bottom: 30px dashed #fff
}
/* width & height */
.arrow1,
.arrow1:after {
position: relative
display: inline-block
width: 0
height: 0
border-top: 0
border-left: 30px dotted transparent
border-right: 30px dotted transparent
border-bottom: 30px dashed #000
}
.arrow1:after {
position: absolute
left: -26px
top: 2px
content: ''
width: 0
height: 0
border-top: 0
border-left: 26px dotted transparent
border-right: 26px dotted transparent
border-bottom: 26px dashed #fff
}
/* border & after */
.arrow2 {
position: relative
display: inline-block
width: 28px
height: 28px
border: 0
border-top: 2px solid #000
border-right: 2px solid #000
-webkit-transform: translate(7px, 14px) rotate(-45deg)
-ms-transform: translate(7px, 14px) rotate(-45deg)
-o-transform: translate(7px, 14px) rotate(-45deg)
transform: translate(7px, 14px) rotate(-45deg)
}
.arrow2:after {
position: absolute
left: 0
top: -2px
width: 42px
height: 2px
content: ''
border-radius: 2px
background-color: #000
-webkit-transform-origin: left top
-moz-transform-origin: left top
-ms-transform-origin: left top
-o-transform-origin: left top
transform-origin: left top
-webkit-transform: rotate(45deg)
-ms-transform: rotate(45deg)
-o-transform: rotate(45deg)
transform: rotate(45deg)
}
</style>
<span class="arrow"></span>
<span class="arrow1"></span>
<span class="arrow2"></span>
</body>
</html>
希望能帮到你，如有疑问请追问，望采纳~
