Part of an inner-city Brisbane street will be permanently closed to vehicles at the end of September as the state's Cross River Rail project begins construction.

Albert Street between Mary and Charlotte streets, in the heart of the CBD, will become a pedestrian-only boulevarde before construction of an underground station for the railway.

A design concept of the Cross River Rail's Albert Street station.

The planned Albert Street station will be on the corner of Mary Street, and will funnel thousands of people underground every day to the new railway.

Cross River Rail Delivery Authority chief executive Graeme Newton said the 120-metre street section had one of the lowest levels of vehicle traffic in the CBD.