The present work aims to improve the performance of tubular solar still by introducing a new design is conducted. A proposed modified tubular solar still is prepared by modifying the design of trough in the shape of half two concentric cylinders integrated with cylindrical parabolic concentrators (CPC). In the modifying design, the trough was proposed in the form of half two concentric cylinders of increases the absorbing surface area of the solar radiation. Besides, the CPC was used to increase the intensity of the solar radiation falling on the absorbent surface. Also, the effect of saltwater layer thickness between the half two concentric cylinders on the performance of modified tubular still was studied to obtain the optimal saltwater layer thickness. A different saltwater layer thickness was studied and compared to the traditional tubular still with a rectangular trough to obtain the optimal design. Experimental results showed that the improvement in accumulated productivity of the modified tubular still reached to 87.9%, 90.8%, 81.9%, and 68.1% for the saltwater layer thickness 1, 2, 3, and 4 cm, respectively compared to traditional tubular still with a rectangular trough. Also, the daily efficiency of modified design reached 60.4%, 61.4%, 58.5%, and 54.1% for the saltwater layer thickness 1, 2, 3, and 4 cm, respectively. But for the traditional case, the daily efficiency reached 32.2%. It is clear that the modified design of tubular solar still is more effective, and the optimal thickness of the saltwater layer between half two concentric cylinders is 2 cm.