In the present work the properties of lightweight cement mortar using porcelinite stone as fine aggregate are studied. Porcelinite stone used as fine aggregate to produce lightweight cement mortar with good compressive strength. The porcelinite stone treated with Sodium Hypochlorite to improve the mechanical properties of this lightweight stone. The results show a significant improvement in the mechanical properties of cement mortar and decreasing in absorption of porcelinite stone with small increasing in density less than 8%.