Abstract: The intensity of Rayliegh-Bénard convection in a fluid layer dispersed with phase-change-material particles was studied. Instead of using the conventional mean temperature method, two new methods were proposed for evaluating the intensity of convection in a horizontal fluid layer with strongly variable apparent specific heat. One method was by introducing a modified Ste number in a Nu-Ra correlation or using the integrally averaged specific heat over the layer in calculating the Rayliegh number. The other method was by using the supercriticality (Ra/Ra_c) as the intensity parameter. The critical Rayliegh number Rac could be calculated with the linear stability theory. After giving two kinds of correlating functions of non-dimensionalized apparent specific heat functions with respect to temperature, the influences of their amplitudes and phase angles on the critical Rayliegh number were investigated. Results showed that the two proposed methods were more rational comparing with the convectional method. The optimum convective mode predicted by the two methods was in agreement with previous experimental results.