Real Madrid's revenues of 480m euros (£401m) topped the Deloitte league table of the world's richest football clubs for the seventh straight year.
Deloitte's Football Money League, based on data for season 2010/11, says Real will match Manchester United's eight-year record if they stay top next year.
Real's arch-rivals Barcelona remained in second place, ahead of Manchester United, who stayed third.
Bayern Munich, Arsenal and Chelsea are fourth, fifth and sixth respectively.Unchanged at top
The top seven clubs stayed in exactly the same positions as in the previous year.
Aston Villa fell out of the league entirely, failing to hold on to their 20th position and leaving English clubs holding six places out of the top 20.
Liverpool fell one spot to ninth place in this year's list.
All of the 20 clubs in the list are from the "big five" European leagues, with Italy contributing five clubs, Germany four, Spain three and France down to two, from three in the previous year.
Together, the top 20 clubs earned 4.4bn euros, a rise of 3% on the previous year.Spanish rivals
Nine of the 20 clubs saw their revenues grow in double digits in 2010/11.
Although seven of them saw a fall in revenue, the authors said that this was mostly down to weaker on-pitch performances, causing falls in ticket sales and merchandising, rather than the effect of weakness in eurozone economies.
Barcelona's shirt sponsorship deal with the Qatar Foundation is worth about 30m euros per season, according to the report.
This, coupled with the club's 3.5m-euro prize money for winning the Fifa World Cup, may enable the Spanish club to catch up with its arch-rival Real next year, the report suggests.
Both Spanish clubs are approaching record revenue levels of 500m euros and may top this in the next few years, says the report.
German club Schalke leapt six places to 10th after a strong performance in last year's season, which took the club to the semi-final in the Uefa Champions League.
In next year's report, however, Schalke will be edged out of the top 10 by Manchester City, say the report's authors, after considering City's heavy financial support from Abu Dhabi investors and its participation in the 2011/12 Champions League.
FOOTBALL FACTS
The top 20 clubs together earned 4.4bn euros
Nine of the top 20 clubs saw double digit growth in income
Barcelona's shirt sponsorship deal is worth about 30m euros per season
Real and Barcelona are both approaching 500m euros in revenue per year
Deloitte Football Money League
1. Real Madrid: 479.5m euros
2. Barcelona: 450.7m euros
3. Man Utd: 367m euros
4. Bayern Munich: 321.4m euros
5. Arsenal: 251.1m euros
6. Chelsea: 249.8m euros
7. AC Milan: 235.1.m euros
8. Internationale: 211.4m euros
9. Liverpool: 203.3m euros
10. Schalke: 202.4m euros
Source: Deloitte: 2010-11
