Brown, who helped the United States to Olympic gold in 1996 and bronze in 2000, replaces Peter Suk, who returned to South Korea in September.
"Britain has some outstanding archers, many with the potential to win medals at the London Games," said Brown.
"Nothing will give me greater pleasure than being the coach that helped them do that. I want to use my experience to the benefit of the British squad."
California-based Brown already has experience helping archers to Olympic gold medals on home soil.
He coached Justin Huish to individual gold as part of the US team in Atlanta in 1996, then took his country's men's team to bronze in Sydney four years later.
He has also coached the US team at four World Championships.
"I have extensive international coaching experience and am very proud of the success I have had in these positions," he added.
We have hired a
coach with a fantastic track record in Olympic success
SymingtonArchery GB performance director
"I feel I am
for this position and extremely
"I am confident Lloyd can bring out the very best in our elite archers, and make them very competitive at the London Olympics.
"I am also sure Lloyd will be a great asset to our up-and-coming archers, such as those on the fringe of the senior squad, over the next three years."
Brown's predecessor, Suk, served as head coach of the GB squad for four years.
Under Suk, Britain won three World Championship medals in Leipzig in 2007, but returned from the 2008 Beijing Olympics empty-handed.
The British women's team lost out to France for the bronze medal in Beijing, while no individual competitors made it past the last 16.
At the time, British competitor Alan Wills was critical of Suk's methods, though Wills later sought to clarify his remarks.
'' Peter Suk has done amazing things
for British archery
but not everyone has the same
"The way our coach works, he is trying to subdue you sometimes," said Wills in the aftermath of defeat by Cuba's Juan Carlos Stevens, which ended the last British hope of an Olympic medal.
"I feel like my personality is being squashed down and hidden away. I need to get a bit aggressive and get pumped up."
However, Wills later said he had spoken "in the heat of the moment" and played down his comments.