The 22-year-old earned $35,719,902 (£22.7m) in 2011 from a combination of music sales, royalties and touring.
Irish rockers U2 took second place with $32m (£20m) thanks to their 360 tour, seen by more than seven million people.
Kenny Chesney came third, followed by last year's highest earner, Lady Gaga, while Adele came 10th.
The British singer had the biggest-selling album of the year, but her earnings were affected by the cancellation of her North American tour for throat surgery.
Nonetheless, she earned $13,081,909 (£8.3m) in 2011,Billboard reported.
U2 claimed the runner's-up position without releasing any new material in 2011, highlighting the importance of tour revenues.
Kenny Chesney also made the bulk of his $29m (£19m) earnings from touring, although he also did well from merchandising and sponsorship.
Source: Billboard
Lady Gaga sold 2.8m albums in the US last year, with 1.1m copies of Born This Way sold in its first week of release.
Her live earnings dropped, however, after the Monster's Ball tour wrapped up in May.
In total, the theatrical pop diva made $25m (£16m) in 2011.
Fifth place was taken by rap star Lil Wayne, who returned to the limelight after serving an eight month jail sentence for gun possession.
His $23m (£14.8m) earnings came from sales of his comeback album Carter III, as well as touring and profits from his record label Young Money Entertainment, home to artists including Drake and Nicki Minaj.
British musicians were well represented on the annual Billboard chart, with Sade in sixth place, Elton John at 13 and Rod Stewart at 29.
Sir Paul McCartney claimed 25th place on the list, despite playing just six concerts in the US last year. The $18.6m (£11.8m) ticket sales earned the musician an estimated $6.2m (£4m), Billboard said.
Sir Paul's former band The Beatles came one place above him, whose back catalogue sales earned an impressive $6.7m (£4.2m) in 2011, thanks largely to their belated appearance on iTunes and other digital music stores.
The band sold 4.7m digital tracks last year - with George Harrison's Here Comes The Sun the most popular download.
Country star Taylor Swift has beaten Adele and Lady Gaga to be named the highest-earning pop artist of 2011 by trade publication Billboard.