Water sorption of dental composites affects dimensional stability, mechanical properties and bonding strength with tooth structures. The diffusion coefficient of water through the resin should be identified. Methods: Ten new composites fillings (M1-M10) were prepared from new Fluoroaluminosilicate powder composition and BisGMA/TEGDMA together with the related compounds such as tri ethylene glycol dimethacrylate, N,NDimethyl amino ethyl methacrylate and Camphorquinone. Five disk shapes were prepared for each composite using a stainless steel mold 15 mm in inner diameter and 1 mm in thickness, according to ISO 4049, the curing of each composite disk for 40 sec. Each disk was immersed separately in water for 90 day all at (37 ±1). Water sorption and solubility were calculated by using these measurements, Diffusion coefficients were also measured with the solution of Fick’s second law. Results: The water sorption (g/mm3) after 90 day immersion ranged from 14.98 g/mm3 (±0.90) for M10 to 36.81g/mm3 (±0.46) for M6. The solubility ranged from 3.3 g/mm3 (±0.90) for M6 to 8.55 g/mm3 (±0.31) for M7, the equilibration time for water sorption was reached at 20 day. M6 had the highest diffusion coefficient 6.25 ×10-9 cm2/s (±3.46). Conclusion: This investigation revealed that M6 composite filling was the best one due to the lowest water solubility while the other investigated fillings showed moderate to high solubility values but all are in accordance with the International Standard ISO 4049.