A focusing and tracking method and system for use on the read/write head of an optical drive is provided. The focusing and tracking method and system is capable of detecting both the focusing error and the tracking error of the read/write head to thereby control the focusing and tracking of the same during read operation. In particular, this focusing and tracking method and system combines the use of a knife-edge focusing method and a push-pull tracking method respectively for focusing and tracking of the read/write head. A specially designed photo detector is used to obtain both the focusing error signal and the tracking error signal. This allows the focusing and tracking system to be simplified in structural complexity, thereby saving manufacturing cost. Moreover, since the focusing error signal and the tracking error signal are obtained respectively in perpendicular directions, the undesired effect of cross-talk between the two error signals can be avoided.