I want to do my post graduation in physics subject in iit's. How to prepare for it??

Hello,
Yes you can do MSc. in physics in best IITs.You have to appear for an exam called IITJAM which is conducted every year to give admission to candidates in MSc. courses.You have to prepare for this exam very well through the books.You can purchase sample papers and solve it to get knowledge about how the questions comes in it.Solve previous years questions too.You can refer:

• Name of book         Author

Intro to quantum mechanicsDavid Griffith
Quantum Mechanics: Concepts and ApplicationsNouredine Zettili
Quantum Mechanics (Schaums Outline Series)Yoav Peleg, Reuven Pnini, Elyahu Zaarur, Eugene Hecht
Introduction to Solid State PhysicsCharles Kittel
Elementary Solid State PhysicsOmar
Solid State PhysicsS. O. Pillai
Statistical PhysicsReif
Mathematical Methods for Physics and EngineeringRiley, Hobson, Bence
Mathematical Methods for PhysicistsArfken
Classical MechanicsHerbert Goldstein
Classical MechanicsJohn R. Taylor
Introduction to Classical Mechanics: With Problems and SolutionsDavid Morin
Heat and Thermodynamics Mark Zemansky
Thermodynamics Kinetic Theory and Statistical ThermodynamicsF.W. Sears, G.L. Salinger
OpticsGhatak
A Text Book of OpticsBrijlal and Subhramanyam
Introduction to ElectrodynamicsGriffith
Electronic Devices and CircuitBoylestad / Nashelsky
Nuclear Fission and Cluster Radioactivity: An Energy-Density Functional ApproachM.A. Hooshyar, Irwin Reichstein, F. Bary Malik
Nuclear PhysicsV. Devanathan
Atomic and Molecular PhysicsRaj Kumar