A spokesman from the force said the 63-year-old was being held on suspicion of rioting and conspiracy to wound with intent.
Police sources said he was one of the “white-shirted men”.
At least 45 people were injured when dozens of men, clad in white T-shirts, indiscriminately attacked bystanders and passengers at the MTR station.
Police have so far arrested more than 60 people in connection with the rampage, including alleged gang members as well as victims of the attack.
Last month, the District Court jailed seven attackers to up to seven years in prison after they were convicted of committing offences including rioting, wounding with intent and conspiracy to wound with intent.