Johnson will launch the review on Thursday alongside the Met commissioner, Bernard Hogan-Howe, which is due to report in the autumn.
In 2008 the mayor commissioned a “Race and Faith” inquiry looking into racism in the force. As a result of the inquiry, the Met said it would open up senior positions to people from different backgrounds, even if they had not started working as a constable.
The report also said it should be easier for staff to apply for internal promotions and transfers.
Johnson said he wanted the force to “build better relations with the communities it serves”.