Toys - including an imitation Star Wars set - which were copied from Lego blueprints were seized, a police statement said.
Police in China say they have uncovered a gang accused of manufacturing and selling 27 million euros worth of counterfeit Lego.
Officers raided a toymaker in the city of Shenzhen and arrested four people.
The toys - including an imitation Star Wars set - were copied from Lego blueprints, a police statement said.
More than 630,000 finished products were seized, the statement added.
"In October 2018, the Shanghai police found that Lepin building blocks available on the market were extremely similar to that of Lego," police said.
Images posted by Chinese authorities following the raid showed products that appeared to be almost identical to those produced by the Danish toy giant.
Along with the apparent Star Wars imitation, products were released in conjunction with the new "Lego Movie 2" and sold under the name "The Lepin Bricks 2", police said.
The fakes were reportedly being sold at a fraction of the price, with a small city-themed Lepin set on the market for 2.5 euros a box, whereas similar Lego sets start at 12 euros.
The raid comes as China seeks to strengthen intellectual property rights, with the number of trials hitting a record high last year.
Meanwhile, Lego last year celebrated a return to growth following a first fall in sales and profits for 13 years in 2017.
The company's bricks and kits are manufactured in five countries - Mexico, China, the Czech Republic, Hungary and Denmark.
Lego sells 75 billion bricks annually in over 140 countries.