US bosses earn an average $11m (£6m; 8.7m euros) per year, representing a salary 262 times the average worker's.
Executives have earned more even as shares have fallen
The average worker's annual earning was just below $42,000, showed findings from the Economic Policy Institute (EPI), a think-tank.
Chief executives made more money in one working day than an average worker made in a year, the research showed.
The gap is the second biggest in 40 years. In 1965 bosses were earning just 24 times the average worker's pay.
The only time this year's figure was beaten was in 2000, when the ratio hit 300.
Back in 1965, the heads of major US firms earned 24 times more than the average worker.
The EPI calculated chief executives' earnings to include salary, bonus and shares. Pay for workers was based on hourly wages.
Executives' pay has been a controversial issue in recent years as shares have fallen in value even as multi-million dollar bonuses have been given to top executives.
Chief executives of the 11 largest firms earned $865m over the past two years, while shares fell by $640bn, a study from Corporate Library, which researches pay and compensation data, recently showed.