The X Factor champion reached the feat just two days after his winner's single 'Impossible' was made available to download.
The track has currently sold over 255,000 copies up until midnight on December 12, which has surpassed Cheryl Cole's first-week total of 152,000 for 'Call My Name' back in June.
The feat also means Arthur has already out-sold last year's winners Little Mix by 45,000 copies, according to The Official Charts Company.
The 2011 X Factor track 'Cannonball' sold 210,000 copies during the entire first week of it being on sale last December.
Arthur's total so far looks set to exceed Leon Jackson's 2007 winner's single 'When You Believe', which shifted 275,000 copies during its opening week.
Only three X Factor winning singles have sold over 500,000 copies during their first week on sale.
Leona Lewis sold 571,000 of 'A Moment Like This' in 2006, Alexandra Burke shifted 576,000 of 'Hallelujah' in 2008 and Shayne Ward sold 742,000 copies of 'That's My Goal' in 2005.
Watch Digital Spy's interview with James Arthur below: