效果演示

Code
<div class="searchBar">
<div class="icon"><i class="iconfont icon-sousuoxiao"></i></div>
<div class="textInput">
<input class="inp" type="text" placeholder="请输入搜索关键字">
<button class="goBtn">go</button>
<div class="clear"><i class="iconfont icon-close"></i></div>
</div>
</div>
* {
margin: 0;
padding: 0;
box-sizing: border-box;
}
body {
width: 100vw;
height: 100vh;
background: linear-gradient(to bottom, skyblue, #003462);
display: flex;
justify-content: center;
align-items: center;
}
.searchBar {
width: 60px;
height: 60px;
background-color: #fff;
box-shadow: 0 0 10px rgba(0, 0, 0, .4);
border-radius: 60px;
position: relative;
overflow: hidden;
transition: .5s;
}
.icon {
width: 60px;
height: 60px;
display: flex;
justify-content: center;
align-items: center;
cursor: pointer;
}
.icon i {
color: dodgerblue;
font-size: 30px;
}
.textInput {
width: 320px;
height: 60px;
display: flex;
justify-content: center;
align-items: center;
background-color: blue;
position: absolute;
top: 0;
left: 60px;
}
.textInput input {
width: 100%;
height: 100%;
border: none;
outline: none;
font-size: 18px;
}
.clear {
width: 15px;
height: 15px;
position: absolute;
right: 22%;
top: 50%;
transform: translateY(-50%);
cursor: pointer;
display: flex;
justify-content: center;
align-items: center;
}
.clear i {
color: #999;
}
.goBtn {
width: 12%;
height: 60%;
position: absolute;
top: 20%;
right: 0;
border-radius: 8px;
outline: none;
border: none;
color: #fff;
box-shadow: 0 0 2px rgba(0, 0, 0, .4);
background: linear-gradient(skyblue, deepskyblue);
cursor: pointer;
}
.changeWidth {
width: 400px;
}