Abstract: In this paper, the thermal efficiency for system horizontal solar concrete collector is studied. Consisted of four models of horizontal concrete solar collector at area 0.6m2 . In addition, the operating conditions were three radiation values of 400W/m2 , 700W/m2 and 1000W/m2 with three fluid inlet temperatures of 15, 20 and 25°C. Models were represented in the Ansys Software 18- workbench with suitable boundary condition according to case model. The models are designed to give the best efficiency at Reynold 900.The case stet up was validated with of the previous work and the results showed a good agreement with error than 6%.The results show that, the best type of tube section was rectangular section are where the thermal efficiency enhancement about 36 % compared to those in the solar collector that contains circular tubes.