Abstract: Soil cation exchange capacity (CEC) is a crucial indicator for assessing soil fertility and buffering capacity,playing a pivotal role in regulating the migration and transformation of soil pollutants,particularly bioavailable heavy metals.Accurate determination of CEC is essential for guiding rational fertilization,soil amelioration,and soil ecological conservation.Addressing the limitations of existing soil CEC determination methods,this study systematically optimized the key experimental conditions of the cobalt hexammine trichloride leaching-spectrophotometry method.Through comprehensive methodological evaluation and optimization of critical parameters,including blank sample preparation,acidic soil determination,organic matter interference correction,oscillation frequency,and interference from suspended matter after centrifugation,the method's analytical performance was significantly enhanced.Under the optimized conditions,the limit of detection reached 0.2 cmol⁺/kg,the limit of quantification was 0.8 cmol⁺/kg,and the precision ranged from 0.7% to 2.1% (n=6).Compared to existing methods,this approach shows marked improvements in sensitivity and accuracy.The findings provide reliable technical support and a theoretical foundation for the refinement and revision of standard methods for soil CEC determination.