If you start at the Frankfurt airport, please use S-Bahn S8 or S9 (direction Hanau, Offenbach Ost) to reach Frankfurt central train station.
Then you can take different S-Bahn trains which will lead you all to Messe Frankfurt:
Take the S3 line heading towards Bad Soden or the S4 line heading towards Kronberg, the S5 line heading towards Bad Homburg/Friedrichsdorf or the S6 line heading towards Friedberg/Groß Karben. After two stations you will reach the "Messe" stop. Enter the exhibition grounds at the "Torhaus" entrance.
Alternatively, you can take a taxi from airport to Messe directly. over 7 years agoAnswered by Messe Frankfurt via WorldNomads.com