His debut single Impossible remained in the top spot this week, notching up 917,000 sales in the four weeks it has been released.
Will.I.Am's Scream & Shout (ft. Britney Spears) was another non-mover at No 2, as was PSY's Gangnam Style at No 3.
Bruno Mars rises two places to No 4 with Locked Out Of Heaven and Taylor Swift also rises two spots to No 5 with I Knew You Were Trouble.
Meanwhile, over in the Official UK Albums Chart, Calvin Harris rose to the No 1 spot with his long player 18 Months.
Emeli Sandé dropped one place with Our Version Of Events at No 2 and Ed Sheeran roses 10 places to No 3 with +.
Jake Bugg was up 12 places at No 4 with his self-titles album and the top five was rounded out by Bruno Mars with Unorthodox Jukebox.
The Official UK Top 10 Singles...
1 (1) James Arthur - Impossible
2 (2) Will.I.Am - Scream & Shout (ft. Britney Spears)
3 (3) PSY - Gangnam Style
4 (6) Bruno Mars - Locked Out Of Heaven
5 (7) Taylor Swift - I Knew You Were Trouble
6 (4) Olly Murs - Troublemaker (ft. Flo Rida)
7 (12) Rihanna - Stay (ft. Mikky Ekko)
8 (8) Rihanna - Diamonds
9 (11) Swedish House Mafia - Don't You Worry Child (ft. John Martin)
10 (10) Labrinth - Beneath Your Beautiful (ft. Emeli Sandé)
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