Mysore to Bangalore road distance is about 140km. The most frequent option to travel from Mysore to Bangalore is bus, followed by train.
Well, other options are like driving all the way to Bangalore or even there is a flight connection between Mysore and Bangalore.
Mysore to Bangalore by Bus: Get to the KSRTC bus station in the city center. Every 5 minutes or so a bus leaves for Bangalore. There are Airavat (a/c volvo bus) and Rajahamsa type buses, Airavat being the expensive luxury type. And of course there is the cheaper Sarige type buses too operate to Bangalore.
All buses leaves from the same bus station (KSRTC bus stand) , from near the northern entrance. You can easily spot this as there is a grandiose arch at the traffic circle, next to the northern entrance of the KSRTC bus station.
Also there is no need to book in advance, as the seats are filled on a first come first served basis. It's about 3 hours to Bangalore. Some buses halt at midway towns like Mandya, the rest halts only at Bangalore.
Also keep in mind, most of the buses go only up to the KSRTC Satellite Bus Station, in the southern outskirts of Bangalore. The Bangalore city center (like the Bangalore city railway station) is a good, 1 hour journey from this bus station.
Some of the buses (esp. the long distance ones) goes to the Majestic Bus Stand (across the Bangalore City Railway Station). If you are specifically interested, ask before you board.
Also if you are planing to fly out of Bangalore, get one of those Mysore to Bangalore Airport direct buses.
Mysore to Bangalore by Train: The greatest advantage of train over bus to Bangalore from Mysore is , the trains can get you to the city center. Trains typically get over crowded, esp the morning and evening trains from Mysore (Station Code:MYS) to Bangalore City (Station Code: SBC)
There are express and passenger trains. Shadabdi Express is the fastest and expensive. If you want to travel tight, catch one of the passenger trains. That has the cheapest fare between Bangalore and Mysore.
Also there is an interesting train between Mysore and Bangalore, nick named 'Night Queen Passenger'. This is an over night passenger train with sleeper coach attached. Of course you can reserve for the berth (www.irctc.co.in) or buy unreserved ticket at the railway station.
Mysore to Bangalore by Road: Well, this is about driving all the way to Bangalore from Mysore. Hit the Nilgiri Road ( the one that goes near the KSRTC bus stand) or any other road that heads to wards Srirangapatna. This is popular SH17 connecting Mysore with Bangalore.
You can also get to the Outer Ring road, that almost encircles Mysore City. The Ring Road crosses SH17 in the outskirts of Mysore, near the Colombia Asia Hospital signal.
So the Mysore-Bangalore road route is like this : Mysore City – 13km ->Srirangapatna- 22km -> Mandya– 20km -> Maddur – 30km ->Ramnagara– 50km -> Bangalore City
Flight connections from Mysore to Bangalore: Spice Jet operate daily (except on Tuesdays & Saturdays) flights to Bangalore & Chennai. The airport is about 10km from the city.