You have to find the control of that dropdown in code behind.
then bind that dropdown as usual you bind dropdown.
You can find Dropdown like:
DropDownList drp=GridView1.FindControl("dropstatus");
Now drp is your DropDown which is inside GridView.
Now bind drp.
like
if ds contain your dataset with records then
drp.DataTextField="Name";
drp.DataValueField="1"
drp.DataSource=ds;
drp.DataBind();