用Task试试：

static void Main(string[] args)
{
//测试数据
List<News> lisNews = new List<News>
{
    new News {id = 1,title = "新闻1", content="新闻内容1",date = DateTime.Now},
    new News {id = 1,title = "新闻2", content="新闻内容2",date = DateTime.Now},
    new News {id = 1,title = "新闻3", content="新闻内容3",date = DateTime.Now},
};
List<Task<string>> tasks = new List<Task<string>>(lisNews.Count);
foreach (var item in lisNews)
{
    //使用任务
    var taskd = new Task(CreateHtml, lisNews);
    taskd.Start();
}
Console.ReadKey();
}
/// <summary>
/// 生成HTML
/// </summary>
/// <param name="obj"></param>
public static void CreateHtml(object obj)
{
    List<News> lisNews = obj as List<News>;
    //TODO:生成HTML
}