This comes as 50 business leaders back the economic case for a second crossrail for the capital, expressing how "vital" it is to securing new homes and jobs.
In an open letter to The Times newspaper, UK businesses said how important Crossrail 2 is to the UK economy, calling on the government to use the current Comprehensive Spending Review to develop the funding needed to start the project early.
The Growth Commissions will, says Johnson, help maximise the benefit of the new railway by bringing together the London boroughs, county councils outside London and key businesses and development stakeholders along the route to work together to ensure the project supports house building and job creation.
The mayor said: "Major projects take time to plan and prepare and with Crossrail 1 nearing completion, we must move quickly to the next transformational growth project which could see even more benefits delivered.
"Crossrail 2 will support up to 200,000 more homes and jobs, adding billions of pounds to the national economy and ensuring a prosperous future for the whole country."
Sir Merrick Cockell has been appointed as the chair of the Growth Commission.
He said the new line is "imperative to the future growth of the capital" as well as across the UK.
"The Growth Commission will play a key role in helping ensure local development plans along the route meet their full potential," Cockell added.
A public consultation is due to start in the autumn.