The crash happened on Sunday lunchtime, when the police car was answering an emergency call. The train involved was a local service.
The accident happened at an unmanned railway crossing between the villages of Smedstorp and Lunnarp. Skåne Police had no more information about the circumstances surrounding the accident.
The dead policeman, who was 55, was airlifted to hospital in Lund together with his 48-year old colleague, who is seriously injured.
Both men were based in Ystad, according to Ewa-Gun Westford, police spokeswoman in the town.