Recent cosmological observations strongly indicate that the universe is dominated by an unknown form of energy with negative pressure. The sim- plest way is to view the cosmological constant as the dark energy. How- ever, a dynamical scalar ‾eld, quintessence, pervading the universe can also act as the dark energy and provide some interesting properties. We will study one of the prevailing quintessence models, the tracker potential, in this paper and use supernovae type Ia (SNIa) data and the acoustic peaks of cosmic microwave background (CMB) anisotropies to constrain the tracker quintessence model.