Abstract: The boron in soil samples is volatile in the acid soluble system, and potassium and sodium cannot be determined simultaneously by the alkali fusion method, the interference of salts also hinders detection. In the HCl-HF-HNO₃ tri-acid system, the addition of mannitol can protect boron from volatilization loss under sealed digestion conditions. Using inductively coupled plasma emission spectrometry (ICP-OES) as the testing method, and employing a hydrofluoric acid-resistant sampling system, contamination of the elements to be tested was effectively prevented. By pre-adding an internal standard to correct volume deviations, the simultaneous determination of boron, phosphorus, sodium and potassium in soil samples can be achieved. The experimental results indicated that in the absence of a stabilizer, boron suffers severely loss due to volatilization during digestion. However, in the presence of a stabilizer, no measurable volatilization loss of boron was observed even above 160 ℃, proving that the use of mannitol as a stabilizer was feasible. By testing and verifying with certified soil and aquatic sediment standard samples, the relative deviation of test results from the recommended values was less than 10% for soil samples with boron content higher than 10 mg/kg. The method has a good sensitivity, simple operation, and can be suitable for large-scale testing tasks.