This paper is a contribution to the valuation of the millet stalk fiber as insulation material in building. To do this, the millet stem is crushed in two sizes and each size obtained is mixed with different Arabic gum content, which acts as a binder. Arabic gum is an effusion of sap from a trunk of acacias from Senegal. This material is still unusable largely because a big quantity is thrown in the nature. The influence of millet stem size and Arabic gum content on mechanical and thermal properties was evaluated. As for the resistance in flexion, we found a null value for all the samples. The compression resistance of samples varies from 0.8 to 1.5 MPa with a percentage of the binder evolving from 3 to 11.27 %. These values of the mechanical resistance are in strong proportionality with the binder dosages. The thermal conductivity varies from 0.113 to 0.914 W. m-1. K-1 with an effusivity going from 228 to 183 J.m-2. °C-1.s-1/2. The results showed that the conductivity and the effusivity increase with the content by linking of the material.