A new method is presented to analyse an exothermic or endothermic process with temperature modulated differential scanning calorimetry. The response of exo- or endo-thermic process against temperature modulation has been directly taken into account in an apparent heat capacity difference of complex quantity. Utilizing the shift in phase lag between sample temperature and heat flow, the specific heat during the transformation process and the temperature coefficient of the transformation rate, e.g. crystal growth rate, are obtainable by the analysis under a reasonable assumption. The applicability of the present method has been examined with the experimental results of polyethylene crystallization.