The invention relates to a dielectric spectrum-based soil in-situ nutrient quick test method. The method comprises the following steps: determining an air value, a water value, a dry soil value and a soil value of a test soil sample column by using a multi-spectral nutrient sensor at various frequency bands; performing water and fertilizer integrated irrigation by using the test soil sample column to simulate drop irrigation until the sample column soil is saturated; after the water and salt is transported for 24 hours, calculating to obtain an original water content value according to the original base data and a regulated capacity salt-base output ratio of each frequency band according to the values of various frequency bands VSIC (a to d); measuring a water content value, an ECe value, a temperature value and each effective-state nitrogen phosphorus and potassium content of the soil; and when the water content is lowered to about 5 percent, repeating the steps, fabricating a soil water content calibration curve and a soil nutrient calibration curve, and completing one-time determination process. By adopting the method, the water content, the total salt content, the acidity, the alkalinity, the temperature and the effective-state nitrogen phosphorus and potassium content can be simultaneously measured, the content of a single-salt ion in the soil of different textures can be dynamically monitored, the soil is not disturbed, and the universality is high.