I’ve been working with the dhtmlxGrid and subgrids and found that when the width of the subgrid is larger than the width of its parent grid (due to the number of columns or the default column widths), a horizontal scrollbar appears on the subgrid. When this occurs, the height of the subgrid is limited to the header and one row. Any additional rows in the subgrid are rendered on the client; however, you cannot see them in viewport of the subgrid. Also, there is no vertical scrollbar to allow the user to navigate between these rows. I can consistently reproduce this behavior in my development environment. Any help would be greatly appreciated.
If you’ve a solution of this problem please inform me too. 
hey i want to know how to use subgrid will send me the proceedings
Try to enable auto height:
mygrid.enableAutoHeight(true);