The incident occurred when RPF constable, George, questioned the man, who was moving suspiciously in a reserved compartment of the Bangalore-Trivandrum Express at around 4 AM, about his ticket, railway police sources said.
The man, suspected to be a thief, whipped out a knife and stabbed him and also injured a RPF Sub Inspector.
He has been arrested and a knife, pepper spray and chloroform was recovered from his possession.
The incident occurred between Chalakudy and Angamally stations near here.