The configurations of a flash memory having a read tracking clock and method thereof are provided. The proposed flash memory includes a first and a second storage capacitors, a first current source providing a first current flowing through the first storage capacitor, a second current source providing a second current flowing through the second storage capacitor, and a comparator electrically connected to the first and the second current sources, and sending out a signal indicating a developing time being accomplished when the second current is larger than the first current.