The incident took place late last night between the Chandari and Kanpur railway stations, they said.
The woman and her daughter, a student of class nine, were travelling in a general coach of the Howrah-Jodhpur Express.
Some 10 to 15 men started troubling and teasing the woman's daughter soon after the train left Howrah, the police said. They reported the matter to security personnel in the train and the youths were taken away. But, they returned later and again started harassing the mother-daughter duo, they said.
With no help coming their way this time, they jumped off the train in a desperate measure to save themselves, the police said.
The woman and her daughter were found injured and unconscious near the railway tracks and rushed to a hospital.
The woman's husband works at a private firm in Delhi, the official said.
A case has been registered against unnamed accused for assaulting women with intent to disrobe them, criminal intimidation and relevant sections of the Protection of Children from Sexual Offences (POCSO) Act, Superintendent of Police, Railways, Prateep Kumar Mishra said.
A woman sub-inspector and a constable of the GRP have been suspended for failing to extend help to the victims, the officer said.