The man surnamed Han was put in criminal detention on suspicion of intentional homicide Thursday, Xinhua cited the Beijing Municipal Public Security Bureau as sayng.
Han was suspected of lifting the baby from her carriage and hurling her onto the ground in Daxing district.
The suspect and another man also beat up the mother, and said she had blocked the way of their car.
The infant was receiving emergency treatment at a hospital.
Police said Han was once sentenced for theft, while the second man who also had a criminal record had surrendered to police.