The synthesis and characterization of anhydorus $Mg_3 (PO_4)_2$ was investigated. $Mg_3 (PO_4)_2$ is reported to have similar structural arrangements with $Co_3(PO_4)_2$ and $gamma-Zn_3(PO_4)_2$ compounds. The sample was prepared by a new technique which is the reaction of $MgCl_2.6H_2O$ and $Na_3PO_4.12H_2O$ solutions at pH=5.1, which was adjusted by adding concentrated $H_3PO_4$ to the reaction mixture and heating the precipitated product at $600^ circ C$ untill constant weight. The purity of the product was checked by X-ray powder diffraction, IR, density measurement, SEM and DTA analysis. The monoclinic unit cell dimensions of product are a=7.605 (2), b=8.233 (3), c=5.080 (1)$A^circ$ and $beta= 94.19^circ$ (3), which was in good agreement with the reported data for $Mg_3(PO_4)_2$. In the IR spectra, peaks due to $PO_4$ anion of $T_d$ symmetry split because of the monoclinic crystal structure with the space group of $P2_1/m$. The SEM micrographs showed a spongy appearance with cavities. DTA analysis proved that anhydrous $Mg_3(PO_4)_2$ is stable up to melting point which is $1184^circ C$.