Xijiang Railway Bridge in Zhaoqing City was damaged yesterday when the boat travelled beneath it, the Guangzhou Railway group said in a statement.
Sections of the rail track were also damaged.
North and northwestern-bound trains from Guangzhou and Haikou, capital of the Hainan province, have been affected, state-run Xinhua news agency reported.
At least 58 trains have been diverted or rescheduled.
The local rail authority has dispatched a team to repair the bridge.