I want to add workflow on submitted form, when the user submit a form, content author will review the submitted data then he can approve or reject the submitted data.
Is there any way/workaround to achieve this with WFFM?
A simple approach is to use the Form Reports dialog to archive approved form entries and delete rejected ones. This will give your content authors something similar to a daily queue.
If this does not meet your requirements, another option is to use the Create Item save action to create a Sitecore item from the form data. This save action allows you to control the item's template, placement in the content tree, as well as the field mappings. The template's standard values would contain a Default Workflow of your choosing, which would give authors the ability to approve/reject, etc.