In this paper, the crystal structure and hydrogen storage properties of the sodium hydride at different x value (NaHxD1-x, NaHxT1-x, NaDxT1-x; x=0, 0.25, 0.5, 0.75, 1.0) are investigated by using density functional theory within the generalized gradient approximation (GGA). The calculated results of NaH (D, T) are in good agreement with the other theoretical results. It has been found that, densities decreased with the increase of x value, while lattice parameters stay constant. The hydrogen storage properties of sodium hydride were predicted. The density-value x (ρ-x) relationship, the variations of the hydrogen storage properties with different crystal structure were obtained systematically.