prakashp_79,
Avionics is a vast field. It can involve everything from designing circuits to system integration. For circuit design, calculus, differential equations Laplace Transforms, Fourier transforms and statistics are all useful. For system design, probaility and statistics (for reliability and maintainability issues) are useful. Can you be mores specific regarding the aspect ov avionics in which you're interested?
Regards,
Kral