Blends of poly(ether ether ketone ketone)(PEEKK) with poly(ether ether ketone) (PEEK) were prepared by melting mixing, The thermal and crystallization behaviors were characterized by DSC, The Avrami exponent is almost independent on composition and crystallization temperature, but the crystallization rate constant decreases as PEEK is in major phase, The melting point of blends decreases with increasing PEEK content but the equilibrium melting point is not affected by composition.