This paper aims to design and construct an experimental heating plate associating with the conjugate gradient optimization method for simultaneously measuring the thermal conductivity (κ), thermal capacity per unit volume (C) and the thermal diffusivity (α) of samples. The experimental measurement results of carrots indicate that the deviation of κ, C and α is respectively less than 6.26%, 6.73% and 11.17% from the literature, and less than 6.9% from the estimated results of Siebels equation.