Hi Suraj
You can perform inline editing on contacts related to Account by using inline edit mode on page block or by using inlineeditsupport tag of visualforce
first you have to get all the contacts related to particular account id by using standard controller and making its extension.
And then iterate that list of contact by using page block table on which you can perform inline editing
Note:Before that you have to embed your vf page on page layout
hope it may help you: