Six of the suspects were charged with "intentionally causing physical hurt" while a seventh faced charges of harbouring the other suspects, it said.
Lan, a reporter for the Beijing-based China Trade News, was attacked along with a colleague when they went to interview the owner of a small unlicensed coal mine outside the northern city of Datong, in early January.
He died a day later from head injuries suffered in the attack.
His colleague, Chang Hanwen, survived but suffered a broken arm and other injuries.
Earlier state media reports said the mine owner, who is among the six facing charges of intentionally causing hurt, organised a group of people to carry out the assault.
Other unconfirmed reports said Lan may have been trying to extract a bribe from the mine owner in return for not writing about his business.
Whether or not that was the issue in Lan's case, the reports have laid bare the widespread practice of Chinese reporters cutting deals to write positive stories or suppress negative news in return for bribes or promises to buy advertising in their publications.
Despite official condemnation of such practices, journalists and academics say they are often driven by government policies that exert tight political control on content while forcing publications to struggle for revenue.