The present work investigated the solar collector system with triangular longitudinal fins fixed to the absorber surface at different configuration. Four models of collectors were manufactured with different absorber plates made from aluminum material. The experiments were carried out at the winter session in the climate of Iraq-Ramadi city with longitude (43.268) and latitude (33.43). The experiments have used three values from (0.027 to 0.037) kg/s. The results showed that the temperature difference increases gradually until midday and begins decreasing gradually until it becomes zero at sunset. Maximum temperatures difference has been obtained at the fourth type which is (20.6˚C), and maximum efficiency and exergetic efficiency (99.9%), (43.08%) respectively. A comparison has been made with previous works for thermal and exergetic efficiency. The comparison showed good compatibility between results; the percentage of error does not exceed 3%. The results proved that the existence of fins was a good technique for enhancing the thermal performance of double pass solar collector with a non-effective increase in pressure drop.