One of the problems of concrete is its large weight. The use of foam in concrete reduces the weight of the concrete and therefore reduces the dead load of the structure. In this project tried to reduce the weight of concrete by addition of foam and improve the properties of concrete by using Fly-Ash. The main objective of research is to evaluate the physical and mechanical properties of concrete which produced by various percentage of foam and fly-ash, effective parameters on strength, density and its workability. Therefore, after studying on characteristics of foam concrete by samples and trying to increase concrete strength while reducing its weight, compressive and tensile strength and specific gravity will be evaluated. To obtain the optimal percentage of stable foam, different percentages of foam were replaced with sand and then tested with various percentages of fly-ash to achieve better strength. Results show that, the optimal mixture of lightweight concrete in compressive strength, is for the specimen containing 15% fly ash and 10% foam which was obtained 24.7 Mpa in 28 days age. Also the maximum tensile strength for 28 days age, is the concrete with 10% foam, 5% and 15% fly-ash which equivalent to 3.3 MPa.