A study has been made of the effect of thermal history on melting behavior of poly (ether-ether-ketone)(PEEK) and its carbon fiber composites (APC-2) br using differential scanning calorimeter (DSC)．The two samples crystallized and annealed between 200 and 315℃ from the rubbery state or from the melt state exhi-bited a small endotherm peak (T'm) at approximate 10 to 20℃ above the crystalliza-tion and annealing temterature (Tc) and a large endotherm peak (Tm) at 335 to 345℃．The small endotherm peak was attributed to the melting and recrvstallization of the unperfect crystals formed at the Tc．The large endotherm peak was attributed to the melting of the perfect crystals．The results of our study showed that the Tm depe-nded linearly on Tc．The "thermodynamic equilibrium melting point" calculated acco-rding to the literature which is defined bv the intersection temperature of T'm as a function of Tc with the T'm = Tc line．The results of our study demonstrated also that carbon fiber in the composites has a strong effect of perfection on the crystals of PEEK matrix，so that the melting point of composites is higher than that of PEEK resin itself．