A kind of beam-like space deployable truss mast with square batten frames supported by four longerons and two diagonal cables cross laced per face is described. A simple method for deriving mechanics parameters of the mast is presented. Element loads for mast to maintain self-equilibrating structure are calculated. Symbolic equations for the axial, bending, shear, torsional stiffness and bending strength of the mast are derived based on proposed method. Equations derived by simple method are consistent with expressions for the effective continuum mechanics of beam-like truss derived previously based on equivalent continuum method, these equations are helpful for mast preliminary design and mechanics analysis. Influence of mast structural parameters on mast stiffness and strength is analyzed, mast stiffness and strength can been improved by selecting reasonable structural parameters.