I would like to know if there is any similarity between electron positron annihilation and brane anti-brane annihilation? Is it there then can we use electron positron annihilation knowledge to study more about brane anti-brane annihilation and there by string theory?
Yes, the brane-antibrane annihilation is analogous to the electron-positron annihilation. The analogy is closest for the annihilation of a D0-brane (a charged particle) and an anti-D0-brane, of course.
The processes in string theory have more structure and mutual relationships than simple processes in quantum electrodynamics so a meaningful direction of the insights goes in the opposite direction. By looking at string theory, one may gain new perspectives on seemingly mundane processes in simple theories such as annihilation in quantum electrodynamics.