In this research the effect of pure (Ca) element addition in different percents of (0.3,0.6,0.9%) on the microstructure and mechanical properties of Al-Cu-Mg alloy were studied .The Alloys were produced using sand casting and heat treated using (T6) treatment which involve [solution treatment , quenching , artificial aging ], aging process were carried out at 220º C for different periods of time ranging between (5min to5hr).Also the work involves a study on the effect of (Ca) addition on both grain size as well as the resulting phases before and after heat treatment, samples were examined using optical microscope, Scanning Electron microscope ,X-Ray diffractometer and image-J software to estimate the average grain size.The results of hardness and tensile tests for (0.6% Ca) and 4hr aging show the best response as compared with the other alloys. The hardness and strength values have been changed from (78.29HV),(110.57Mpa) respectively during (30min)at 220ºC for (non-Ca) content alloy to(125.9HV),(164.2Mpa) for (0.6%C) alloy. X-Ray diffraction , results shows the basic phase that forms is Al2CuMg (Sˋˋ, Sˋ phase) which is considered as the main strengthening phase in Al alloys, and it was found that (Ca) addition leads to form (Al4Ca) and (Al2Ca) which delay the alloy response to precipitation hardening by delaying the formation of (S)phase. Also (Ca) addition in the range of (0.3- 0.6%) gives the refining effect as shown from image-J results ,While increasing Ca content up 0.9%wt has resulted in a reduction in the grains refining which leads to a decrease in hardness and tensile strength, From these results the decrease in tensile strength with increasing Ca content over 0.9% seems to be attributed to the reduction in elongation caused by the occurrence of micro porosity due to (Ca) addition.