The Danish company found itself at the centre of a social media storm last year after Ai said it had refused his order of the famous children's building blocks as they would be "used for political works".
Ai said he was "flabbergasted" by the decision, and in a social media post appeared to link the refusal to the recent announcement that British firm Merlin Entertainments will open a Legoland theme park in Shanghai.
See also: Lego faces backlash after Ai Weiwei snub
But the Billund-based company made a U-turn on Tuesday, saying that from this month it would no longer ask for the reasons behind large sales to avoid any "misunderstandings".
"As of January 1st, the Lego Group no longer asks for the thematic purpose when selling large quantities of Lego bricks for projects," the company said in a statement.
"Instead, the customers will be asked to make it clear -- if they intend to display their Lego creations in public -- that the LEGO Group does not support or endorse the specific projects."
Ai, China's most prominent contemporary artist, helped design the Bird's Nest stadium for the Beijing Olympics and has been exhibited around the globe, but his works have often run afoul of China's authorities.
He used Lego bricks to create portraits of political activists from around the world during a 2014 exhibition on freedom of expression at the famous US island prison of Alcatraz, in San Francisco Bay.
He also used the building blocks to create artworks for the Andy Warhol-Ai Wei Wei show in Melbourne, Australia, last year after fans from around the world donated bricks in defiance of Lego's refusal to sell to him.
Responding to news of Lego's policy change the artist quipped on Twitter: "Nice move #freedomofexpression."
China has been a key driver of Lego's growth in recent years, and the company opened an office in Shanghai last year in addition to its manufacturing operations in the country.