效果图

超简单，只需一段CSS代码即可实现

/*文章内超链接下波浪线*/
.wp-posts-content a:hover {color:#ff4500;text-decoration:none;background:url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 20 4'%3E%3Cpath fill='none' stroke='%23FF4500' d='M0 3.5c5 0 5-3 10-3s5 3 10 3 5-3 10-3 5 3 10 3'/%3E%3C/svg%3E")repeat-x 0 100%;background-size:20px auto;animation:waveMove 1s infinite linear}
@keyframes waveMove{from{background-position:0 100%}
to{background-position:-20px 100%}
}
/*文章内超链接下波浪线结束*/