The woman, Mandeep Kaur, 30, and her son were travelling in a general coach of the train.
The accused, Sandeep, who was alone in the wagon, started troubling and teasing her as the train crossed Dhamtan Sahib, the police said.
When she resisted, the man allegedly pushed her off the train. Later, as per the police, he also jumped off the moving train.
The accused was found unconscious near railway tracks, by the police. Later, the police came to know about his offence.
Before the crime, the victim called her husband Harjinder Singh and asked him to receive her at the railway station.
As the train reached Tohana, Harjinder Singh found his son weeping, who informed him about the crime.
The police in the morning found the body of the victim lying in fields.
Superintendent of Police Astha Modi told the media that the accused has been booked under Section 302 (murder) and 354 (assault or criminal force to a woman) of the Indian Penal Code (IPC).