To improve the rate of pesticide utilization, reduce pesticide usage, and effectively eliminate the adverse effects of pesticides on the environment, a carrier material was prepared by modifying starch using a one-step irradiation treatment. This carrier material was subsequently loaded with glyphosate isopropylamine salt to synthesize a glyphosate isopropylamine salt slow-release agent. The morphology and composition of this slow-release agent were characterized using scanning electron microscopy and infrared spectroscopy, and the slow-release performance, surface tension, and herbicidal activity of the different drug-loaded systems were also examined. Compared with the unloaded and attapulgite-loaded glyphosate isopropylamine salts, the rate of release obtained using the slow-release agent was reduced by 44.00% and 20.45% at 720 min, respectively. The release equilibrium time of the attapulgite-loaded glyphosate isopropylamine salt was 1 440 min, whereas that of the slow-release agent was 1 700 min. Based on the kinetic analysis and fitting, the first-order model correlation coefficient R² of the glyphosate isopropylamine salt release curve ranged from 0.956 6 to 0.997 2, indicating that the fitting accuracy was high. Furthermore, a comparison of herbicidal activities showed that this glyphosate isopropylamine salt slow-release agent exhibited an improved control effect on barnyard grasses. In summary, the method for obtaining carrier materials by irradiation is simple, efficient, energy-saving, and environmentally friendly. The glyphosate isopropylamine salt slow-release agent synthesized based on this exhibited favorable slow-release performance and herbicidal activity, providing a new approach for the development of slow-release pesticides.