Abu al-Abbas River is one of the tributaries of the Zard River, and its catchment area is located in southwest Iran, Khuzestan province and Baghmalek city. The length of this river is 38.96 km from its source to the confluence with other branches of the Zard River. In this research, the effect of season and ecogeomorphological factors on the water quality of Abu al-Abbas river was investigated. To achieve this goal, agricultural wastewater was chosen as an ecological factor; Also, the physical and chemical parameters of water (DO), COD, ammonia, nitrate, phosphate, sulfate, temperature, EC and PH) were measured at 7 stations along a route of about 10 km in summer and winter of 1400. According to the results, some parameters (COD, NH3, NO3, po44, SO44, and EC) have increased at the intersection of agricultural waste water with river water. Due to the fact that the amount of measured parameters in the sewage stations entering the river is more than the water stations of Abu al-Abbas river, agricultural activities and ecological factors are considered as the main reasons for the relative increase of the mentioned parameters and the pollution of Abu al-Abbas river. Also, the types of geological formations in the basin, such as gypsum (gypsum sulfate mineral) and limestone (calcite mineral) in the path of Abu al-Abbas river increase the amount of salts and decrease the quality of the river water, especially in the winter season due to the washing of the path. In the meantime, seasonal changes due to decrease or increase in precipitation affect the intensity and weakness of these changes. Along with the change of seasons, geological and morphological factors, agricultural activities were identified as the main factors of the relative increase of the mentioned parameters.