Frankfurt car exhibition

Check hotel booking websites (e.g. booking.com or similar), where you can search for hotels based on location, price and other criteria.
Please note that hotels during the car exhibition are likely to be booked up for months in advance (and prices go up, too), especially those near the fairgrounds. But Frankfurt has an excellent public transport system that will get you there comfortably from almost any hotel - or you can take a taxi.

Thanks for your information
Once I get visa I will book the hotel

You'll find that actually, most of the hotels put their prices up at that time of year and the city is fully booked. There are a quite a few low cost hotels though near the Messe and the main station. But you should definitely book now. Don't assume prices will go down last minute. Because they won't :-)

any one can give me the address of Exhibition i want to book hotel near it if i can :-(