<input type="checkbox" name="btn" id="btn1"><label for="btn1">按钮1</label>

input[type="checkbox"]{width:20px;height:20px;display: inline-block;text-align: center;vertical-align: middle; line-height: 18px;position: relative;}
input[type="checkbox"]::before{content: "";position: absolute;top: 0;left: 0;background: #fff;width: 100%;height: 100%;border: 1px solid #d9d9d9}
input[type="checkbox"]:checked::before{content: "\2713";background-color: #fff;position: absolute;top: 0;left: 0;width:100%;border: 1px solid #e50232;color:#e50232;font-size: 20px;font-weight: bold;}