The invention relates to the technical field of agriculture, in particular to a method for measuring potassium ion absorption kinetics of cotton. The method specifically comprises the steps that a cotton seedling is fixed in depletion liquid, and during depletion treatment of 0-1 h, a depletion liquid sample is taken once every 5-10 min; during depletion treatment of 1-h, the depletion liquid sample is taken once every 30-60 min; during depletion treatment of 10-30h, the depletion liquid sample is taken once every 2-4 h, and the concentrations of potassium ions in the depletion liquid samples are measured respectively. Related parameters in the experiment process are optimized, especially the sampling time interval is optimized, and a drawn absorption curve can reflect the potassium ion absorption law of the cotton more precisely. The method is easy to operate and high in precision, the absorption kinetics curve is smooth, and a theoretical basis is provided for accurate screening of the efficient gene type cotton and reasonable application of potash fertilizer.