nested model properties dont work with @Html.EditorFor?

That should work. I cannot repro.

Model:

public class ModelClass 
{ 
    public string Name { get; set; }
    public DetailClass Detail { get; set; }
}

public class DetailClass 
{
    public string Name { get; set; } 
}

Controller:

public class HomeController : Controller
{
    public ActionResult Index()
    {
        var model = new ModelClass
        {
            Name = "model name",
            Detail = new DetailClass
            {
                Name = "detail name"
            }
        };
        return View(model);
    }

    [HttpPost]
    public ActionResult Index(ModelClass model)
    {
        return Content(
            string.Format(
                "name: {0}, detail.name: {1}", 
                model.Name, 
                model.Detail.Name
            )
        );
    }
}

View:

@model ModelClass

@using (Html.BeginForm())
{
    @Html.EditorFor(x => x.Name)
    @Html.EditorFor(x => x.Detail.Name)
    <button type="submit">OK</button>
}

The 2 properties are correctly bound.

If you´re using EntityFramework you should include the child in the query.

For example:

public MyClass getById(int id){
    return DbSet.Include(q => q.Detail).SingleOrDefault(q => q.Id == id);
}

Then when you call your Model the detail will be included. So you can use Name.Detail.Name.