Shan Guoying, one of the restorers, said the repair work was "detailed and time-consuming".
"We have to work six days a week and can only finish two to four parts of the model each day," Shan said.
Clearing dust was the first and most difficult step as the items are small.
Almost all materials used are the same as for the originals: wood for houses and copper wire for trees.
But for the walls of houses, they changed from paper to plastic for durability.
"It was an emotional moment to see the original color being brought back to life, with gray houses and gold for the Forbidden City," Jiang said.
The model will be encased in glass from September, said Zhang Bin, director of the museum, adding that the restoration will cost about 500,000 yuan ($81,800).
Zhang said that the museum planned to use 3-D technology to display the model in the future.
Foreign visitors are also welcome to have a look but they need to apply to the State Archives Administration.
Jiang Rong, the spokeswoman, said the museum will invite experts and residents to submit their memories of old Beijing and help identify some buildings on the model.
"This is good news for those who are interested in old Beijing," a writer, in his 40s, who gave his surname as Zhao, told China Daily.
"The city has experienced drastic changes in the past 60 years and we need more preservation efforts, both physically and spiritually," Zhao said.
Zhang Wei, 36, founded the website Old Beijing and has collected a valuable collection of photos and stories.
The model is valuable because there was little advanced technology to keep the city's historic information decades ago, Zhang said.
"More viewing of the model will mean that it brings more value to the public," he added.
Yan Ran contributed to this story.