Curtis, 22, is a former Stoke and Crewe Alexandra academy player and started his first spell at the EVO-STIK Premier League club in 2014/15.
A serious knee injury picked up playing on loan at Stafford Town in November 2015 ruled him out for the most of the next two seasons, but he returned to the Boro ahead of this season following a spell at Newcastle Town.
A statement on the club’s official website said: “Alex Curtis has been allowed to leave the club in order to get some game time. Alex has not been able to command a first team place after his long term knee injury and Steve Burr has agreed to him joining Sutton Coldfield Town.
“The club wish him well and hope that he can re-gain the form that he has previously shown.”
Sutton Coldfield Town finished bottom of the EVO-STIK Premier League last season, but have now moved in to the Southern League Division One Central.
Stafford Rangers are back in action this Saturday with a trip to Buxton.