The commonly used method for determining exchangeable bases is to repeatedly leach a soil sample with 70% ethanol (CH₃CH₂OH) solution, and then treated with the mixture of 0.1 mol L^-1 ammonium chloride (NH₄Cl) and 70% ethanol (CH₃CH₂OH), 8.5 in pH, several times for extraction, and in the end, content of K , Na , Ca² and Mg² in the extractant is determined, separately. However, this method is complicated and time-consuming in operation and repeated extraction may increase dissolution of carbonate in the soil solution, thus making results of the determination tend to be higher. Based on the above-mentioned, tests were conducted of 10 ion exchangers different in concentration of NH₄Cl and NH₄OAc and in pH for comparison in solubility of carbonates and content of exchangeable Ca² and Mg² . Results indicate that the mixture of 1mol L^-1 NH₄Cl and 70% CH₃CH₂OH, 8.5 in pH is the most suitable one. The new method goes like this, wash a soil sample off salts with 70% CH₃CH₂OH first and then treat the sample with the mixture of 1mol L^-1 NH₄Cl and 70% CH₃CH₂OH 8.5 in pH for extraction, only once, and in the end, concentration of K , Na , Ca² and Mg² in extractant is determined. To sum up, this method not only simplifies the operation procedure, but also effectively inhibits dissolution of carbonate in the calcareous soils, thus lowering deviation of the determination.