The man, aged in his 40s, suffered wounds to his back, chest and neck in the incident on Saturday afternoon.

He was taken to Royal Prince Alfred Hospital in a serious but stable condition.

NSW Ambulance Inspector Dominic Wong said the man was bleeding heavily from multiple torso and head wounds when paramedics arrived just after one pm.

"The medical team worked quickly to control the bleeding and get the patient to hospital," he said in a statement.

"NSW Police and Sydney Trains staff did a great job in securing the scene and providing first aid."

Another man, who was treated at the scene for minor cuts, was taken into police custody.

NSW Police say the pair are known to each other and the stabbing is linked to domestic violence.

"There is no ongoing threat to the community," police said in a statement.

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Australian Associated Press