An experimental method to determine the order degree of isotactic poly(propylene) (iPP) via regularity bands was developed using fast heating Fourier transform infrared spectroscopy. The various regularity bands can be rearranged in terms of the order degree from high to low: 940, 1220, 1167. 1303, 1330, 841, 998, 900, 808, 1100 and 973 cm(-1). When the crystalline iPP melts, partially ordered melt is formed. With a decreasing degree of order of the partially ordered melt, the crystallization peak shifts to lower temperatures and the exothermal enthalpy becomes larger.