In this communication, we have discussed the theory of generalized synchronization of two bidirectionally coupled chaotic systems through linear transformation and have got a transformation matrix in general form. Also we have seen that for a special case the generalized synchronization becomes projective synchronization. We have applied this theory in two bidirectionally coupled Qi and Chen chaotic systems and discussed different cases for different forms of the transformation matrix. Finally numerical simulation results are presented and discussed to verify our claim.