How to add a payment gateway with two different accounts? I want to add two different accounts for a single gateway . Depending  upon Product_id or product_sku value it should use a corresponding account for payment.

How to do it? I have used the Drupal Commerce module.
Use multiple payment method rules for the same payment gateway and add conditions to them that check for the existence of particular products in the order's line items. How you do that is up to you and what your product catalog is like.