html代码

<div class="container">
    <div class="row" id="login">
        <div class="col-lg-4 col-lg-offset-4 col-md-4 col-md-offset-4 col-sm-4 col-sm-offset-4 col-xs-8 col-xs-offset-2">
            <form class="form-horizontal">
                <div class="form-group form-inline">
                    <label for="username"><i class="fa fa-user"></i>用户名:</label>
                    <input type="text" id="username" placeholder="请输入用户名">
                </div>
                <div class="form-group form-inline">
                    <label for="password"><i class="fa fa-lock"></i>用户名:</label>
                    <input type="password" id="password" placeholder="请输入密码">
                </div>
                <button type="submit" id="login_submit">登录</button>
            </form>
        </div>
    </div>
</div>

css代码

label { width:30%;}
input { width:68%; border: none;}
#login_submit{ width:60%;}