The non-isothermal crystallization kinetics were investigated by differential scanning calorimetry for the nylon 6/graphene composites prepared by in situ polymerization. The Avrami theory modified by Jeziorny、Ozawa equation and Moequation were used to describe the non-isothermal crystallization kinetics. The Analysis based on the Avrami theory modified by Jeziorny shows that，at lower cooling rates (at 5, 10, 20 K/min), the nylon 6/graphene composites have lower crystallization rate than pure nylon 6. However, at higher cooling rates (at 40 K/min), the nylon 6/graphene composites have higher crystallization rate than pure nylon 6. The values of Avrami exponent m and the cooling crystallization function F(T) from Ozawa plots indicate that the mode of the nucleation and growth at initial stage of the non-isothermal crystallization may be as follows: two-dimensional, then one-dimensional for all samples at 5~10 °C/min; three-dimensional or complicated than three-dimensional, then two-dimensional and one-dimensional at 10~20°C/min and  20~40 °C/min. The good linearity of the Mo plots indicated that the combined approach could successfully describe the crystallization processes of the nylon 6 and nylon 6/graphene composites. The activation energies (ΔE) of the nylon 6/graphene composites, determined by Kissinger method, were lower than those of pure nylon 6.