Ok Found solution just add string_limit in addcolumn or addColumnAfter function in grid.php
$this->addColumnAfter('addons', array(
'header' => Mage::helper('sales')->__('Addons'),
'filter' => false,
'sortable' => false,
'index' => 'addons',
'type' => 'text',
'string_limit' => '500', /* added for content limit */
), 'billing_name');