要创建一个块级按钮，请使用.btn-block类。
您可以尝试运行以下代码来添加块级按钮-
<!DOCTYPE html> <html> <head> <title>Bootstrap Example</title> <meta name = "viewport" content = "width=device-width, initial-scale = 1"> <link rel = "stylesheet" href = "https://stackpath.bootstrapcdn.com/bootstrap/4.1.1/css/bootstrap.min.css"> <script src = "https://cdn.staticfile.org/jquery/3.3.1/jquery.min.js"></script> <script src = "https://stackpath.bootstrapcdn.com/bootstrap/4.1.1/js/bootstrap.min.js"></script> </head> <body> <p>The following are block level buttons:</p> <button type = "button" class = "btn btn-primary btn-lg btn-block"> Block level Primary button </button> <button type = "button" class = "btn btn-default btn-lg btn-block"> Block level button </button> </body> </html>