The raid, at Beaverbrooks in Hanley on 17 November, saw jewellery and watches stolen.
A 25-year-old man and a 27-year-old woman have already been charged in connection with the raid.
A 36-year-old man was arrested in the Oldham area of Greater Manchester on Friday and a number of homes in the area were searched by officers.
Det Ch Insp Ricky Fields, from Staffordshire Police, said there was a "substantial reward" for information that led to the recovery of stolen items.
A man has been arrested in connection with a £500,000 robbery at a jewellers in Stoke-on-Trent.