Abstract: One kind of new cefazolin sodium hydrate crystal was obtained in the isopropyl alcohol-water system. There are two symmetry independent molecules in the asymmetric unit, both being well ordered in the lattice, and ten independent water positions but generally four to six (mean five) water molecules and one sodium ion present in the unit cell structure. Huge solvent tunnels can be found. Again there are two general regions of water molecules, those in the large solvent tunnels and those in proximity of the sodium ion and the tetrazole moieties of the drug molecule. The physical and chemical characteristics of the new cefazolin sodium hydrate crystal are similar to that of the α-form cefazolin sodium crystal, and the new crystal has better chemical stability than amorphous cefazolin sodium powder.