Hi,
[...] i am going to make, line follower robot,
Which line follower?
Please post a link when you mention something like that - we're good, but we're not psychics
using IR sensor also i m using mobile phone battery, 3.7 (using regulator 3.3 v ) volt and my question is :
Don't use a regulator.
Regulators need voltage to operate. THE LDO variety up to ~1V and the regular types up to 3.5V - neither of them would be very helpful.
The cell phone battery will only be 3.7V when freshly charged and it discharges down to ~3.0..3.3V.
Unless you use equipment that cannot handle 3.7V, you have absolutely no reason to use a regulator and even in the unlikely case, a zener would be the only really useable solution.
did ir sensor work on 3.3 volt perfectly or not,.,
You have to tell us which sensor you are talking about.
using 6 sensor
mobile battery current : 850mA
The motor(s) will probably have the major current draw.
waiting for reply,.,.... 
Now there's a surprise
