Chorley once captained MK Dons and made more than 130 appearances for the club (As Wimbledon and the MK Dons) before joining League One side Gillingham last season.
Chorley, the third signing of the summer, will sign a two year deal if he passes a medical with the club and is believed to be the dominant central defender Ronnie Moore has been looking for.
In other news, Tranmere have also appointed Peter Shirtliff as their new assistant manager after John Breckin left the club for personal reasons at the end of the season.
Shirtliff, a former coach at Barnsley and Leicester as well as the former Mansfield manager has been described as a great addition to the squad by Ronnie Moore.