this is by design and there's no property to disable that space.  however, if you handle the ChartDrawItem or FillSceneGraph event, you should be able to find the Line primitive and extend it as desired.

private void ultraChart1_FillSceneGraph(object sender, FillSceneGraphEventArgs e)
{
    IAdvanceAxis xAxis = e.Grid["X"] as IAdvanceAxis;
    IAdvanceAxis yAxis = e.Grid["Y"] as IAdvanceAxis;

    Rectangle chartLayerBounds = e.ChartCore.GetChartLayer().GetOuterBounds();

    foreach (Primitive currentPrimitive in e.SceneGraph)
    {
        Line currentLine = currentPrimitive as Line;
        if (currentLine != null)
        {
            if (currentLine.p1.Y == currentLine.p2.Y)
            {
                // must be the x axis or an x gridline
                currentLine.p1.X = chartLayerBounds.Left;
                currentLine.p2.X = chartLayerBounds.Right;
            }
            else if (currentLine.p1.X == currentLine.p2.X)
            {
                // must be the y axis or a y gridline
                currentLine.p1.Y = chartLayerBounds.Bottom;
                currentLine.p2.Y = chartLayerBounds.Top;
            }
        }

    }
}

ok, thank you for your suggestion.

 I tried to set Margin.Far.Value and Margin.Near.Value to respectively appreciate data, the problem i mentioned above has been solved.

However, there is another problem. the AxisX and AxisY will never joint since there are margins existing. there is a blank during between both Axises. How could i make the AxisX cross the AxisY at right angles.

 Hope your further help!!