The purpose of this research is to determine the relationship between the land area in the agricultural watershed and the nutrient load in the Ca River basin. Eight sampling sites in the Ca River basin were chosen for sampling in two phases during the dry season (5/2021) and the rainy season (September-2021). The results show that the measured water flow ranges from 27.7 m3/s to 206.1 m3/s in the dry season, with the highest reaching 2696 m3/s and the lowest at 395 m3/s in the rainy season. The load results of nutrients TN and, TP show a close relationship with flow and topography. The area of agricultural land in the basins influences nutrient load, which follows two distinct trends, increasing steadily in the northwest side river group and fluctuating in the southeast side river group. The land use process has a more obvious impact on the load during the dry season, whereas natural factors change the variation of nutrient load flows during the rainy season.