At total of 568 people were freed from slavery in brick kilns and illegal mines in raids on sites in Shanxi and central Henan provinces.
More than 350 people, including 22 children, were freed from 3,700 brick works and coal mines in Shanxi while 217, including 29 children and 10 mentally handicapped people, were released in Henan.
Officials and Communist party members were implicated in the scandal.
Police said they broke up five human-trafficking gangs in the Henan capital of Zhengzhou and had arrested 13 members accused of supplying slave labour.
Forty-eight people were detained in Shanxi while 120 were held in Henan.
The detainees included Heng Tinghan, 42, in Shanxi, who is accused of employing 32 slave labourers at a brick kiln he ran for the son of a local party chief.
One worker at the kiln was allegedly beaten to death last year while others were regularly starved, beaten and forced to work long hours for no pay.