An investigation on a new material composed of magnesium phosphate cement(MPC), fly ash, and rape stalk was presented. The main goal was to evaluate the viability of using this new material as an insulation material for buildings. Several composites with different concentrations and rape stalk sizes were prepared. The density, compressive strength, and thermal conductivity of the material were measured. Experimental results show that the proposed MPC rape stalk concrete possesses required properties for production of lightweight concrete for structural and non structural applications. The physical properties of the rape stalk indicate that it is promising for producing plant concrete. Results also indicate that MPC might be a better cementitious material for producing plant aggregate concrete compared with Portland cement or lime.