通过在.input-group本身中添加.form-group-lg，input-group-sm，input-group-xs之类的相对形式大小调整类，来更改输入组的大小。
您可以尝试运行以下代码来更改Bootstrap中输入组的大小：
<!DOCTYPE html> <html> <head> <title>Bootstrap Example</title> <link rel = "stylesheet" href = "https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css"> <script src = "https://cdn.staticfile.org/jquery/3.3.1/jquery.min.js"></script> <script src = "https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script> </head> <body> <div style = "padding: 100px 100px 10px;"> <form class = "bs-example bs-example-form" role = "form"> <div class = "input-group input-group-lg"> <span class = "input-group-addon">@</span> <input type = "text" class = "form-control" placeholder = "Twitterhandle"> </div> <br> <div class = "input-group"> <span class = "input-group-addon">@</span> <input type = "text" class = "form-control" placeholder = "Twitterhandle"> </div> <br> <div class = "input-group input-group-sm"> <span class = "input-group-addon">@</span> <input type = "text" class = "form-control" placeholder = "Twitterhandle"> </div> </form> </body> </html>