The record surpassed that of Zhang Yimou's 2002 film Hero, which made $34.77m (RMB250m).
Zhang's 2006 imperial drama Curse Of The Golden Flower remains the highest-grossing local production in China so far, with a final gross of $38.94m (RMB280m).
The Assembly is still showing in the county's major cinemas, 40 days after release on Dec 20, 2007. As the film lacks major Asian stars, director Feng Xiaogang did not expect the box office figure to reach RMB200m, or to surpass star-studded blockbuster The Warlords, which was released one week earlier.
The Warlords has also been a major hit in mainland China grossing more than $29m (RMB210m) as of the end of January.
It is understood that The Assembly has won support from the Chinese authorities due to its patriotic themes, which helped boost box office. One day after the film's release, CCTV's prime-time news ran a one minute and nine seconds report on the film and its strong opening, marking the first time that a film has received such attention from a state-owned broadcaster's national news programme.
'The film broke the boundaries between 'main melody' [ie propaganda] films and commercial blockbusters, and found a good balance between the two,' said Beijing Film Academy professor Zheng Dongtian.
UK distributor Metrodome last month acquired UK rights to The Assembly and Feng's 2006 film The Banquet and plans to release them in the spring. Besides the UK, the film was previously sold to Brazil, Eastern Europe and Korea.
The Assembly's mainland internet distribution rights were acquired by Beijing-based Jeboo.com, while Shanghai-based BestTV acquired the IPTV rights to the film.