Train passengers and CityRail staff have helped to subdue a man who allegedly stabbed another passenger in the head following an argument in western Sydney, police say.

The two men, aged 35 and 44 and who were strangers, allegedly started quarrelling while on a train heading towards Cabramatta station on Wednesday afternoon, Chief Inspector Arthur Aleksandrowicz said.

When both men alighted at Cabramatta station, the fight worsened and the older man allegedly used a "small knife" to attack the other man, causing him to receive cuts across his head, police said.

CityRail staff separated the two men and when the alleged attacker dropped the knife during the brawl, a bystander kicked it on to the railway tracks, Chief Inspector Aleksandrowicz said.

CityRail staff and other passengers then helped to hold on to him until police arrived, he said.

The younger man was taken to Liverpool with non-life threatening injuries, police said.

The 44-year-old was taken to Cabramatta police station and charged with wounding with intent.

He was refused bail to appear in Bankstown Local Court on Thursday.