Abstract: This paper introduces fractal and multifractal theory, as well as the application of the WTMM method to compute the multifractal spectrum. Then the multifractal spectrum of the 2-6-2 Cantor Set is analyzed theoretically and by the WTMM method, so that the physical significance of the multifractal spectrum is obtained. The temperature signals of Rayleigh-Bénard convection is analyzed using the WTMM method. It is found that the WTMM is a feasible method to analyze the multifractal spectrum. The multifractal structure of Rayleigh-Bénard convection change gradually from center to edge.