子线程：

procedure TreadThread.Execute;
begin
inherited;
FreeOnTerminate := True;
while not Terminated do begin
////dosomething;
end;
Sleep(100);
end;
end;

主线程：

var
H: array[0..0] of Thandle;
begin
try
H[0] := RCThread.handle;

// 安全退出子线程
RCThread.Terminate;
if MsgWaitForMultipleObjects(1, H, True, 1000, QS_ALLINPUT) = WAIT_OBJECT_0 then begin
//线程已经安全退出
end;
except
on e: Exception do
ShowMessage(e.Message);
end;
end;