Structures and crystal form transition of the novel aryl ether ketone polymer containing meta-phenylene linkage: PEKEKK(T/I) were investigated by wide angle X-ray diffraction (WAXD), imaging plates (IPs) and small angle X-ray scattering (SAXS). The energy of activation of the decomposition reaction and degree of crystallinity of PEKEKK(T/I) were determined by WAXD and thermo-gravimetric analysis (TGA), respectively. Results obtained from WAXD and IPs show that crystal forms coexist in the PEKEKK(T/I) samples isothermally cold crystallized in the temperature range from 180“C to 240T? and only form occurs in PEKEKK(TTI) samples isothermally cold crystallized at 2701C. The radius of gyration (Rg), thickness of microregions with electron-density fluctuations (E) and distribution of particle sizes were investigated by SAXS. Structures and crystal form transition of the novel aryl ether ketone polymer containing meta-phenylene linkage: PEKEKK (T / I) were investigated by wide angle X-ray diffraction (WAXD) imaging plates (IPs) SAXS). The energy of activation of the decomposition reaction and degree of crystallinity of PEKEKK (T / I) were determined by WAXD and thermo-gravimetric analysis (TGA), respectively. Results obtained from WAXD and IPs show that crystal forms coexist in the PEKEKK (T / I) samples areothermally cold crystallized in the temperature range from 180 ”C to 240T? And only form occurs in PEKEKK (TTI) samples isothermally cold crystallized at 2701C. The radius of gyration (Rg), thickness of microregions with electron-density fluctuations (E) and distribution of particle sizes were investigated by SAXS.