As one of the important material basis and natural resources for human survival, the content of nutrient elements in soil is not only the basis of agricultural production but also an important indicator for evaluating soil quality. The traditional method for determining soil nutrient elements is mainly based on liquid injection, which is cumbersome to operate and has certain environmental pollution. In this paper, the ultra-high pressure sample preparation technology is combined with LIBS technology, which integrates the green and pollution-free sample pretreatment technology and the determination technology that is simple to operate and can carry out multi-element synchronous and rapid detection. The analytical method for determining Silico, Aluminum, Iron and Potassium in soil by ultra-high pressure sample preparation and laser-induced breakdown spectroscopy technology is established. The comparative study on the sample preparation pressure found that when the sample preparation pressure is 2 000 kN, the surface of the prepared sample is smooth and flat, with better compactness and the best measurement precision. By optimizing the measurement conditions of the LIBS instrument, we found that the use of multiple location sampling, the laser energy, gate delay, and spot size were 0.80 mJ, 0.5 μs, and 60 μm, respectively, could reduce the influence of thermal effect caused by the ablation of the sample and sample surface unevenness on the measurement results. It increases the signal-to-background ratio of the measurement, thereby increasing the accuracy and precision of the measurement results. Under the optimized conditions of this method, we used the Certified Reference Materials for the Chemical Composition of Soils to do the calibration curve of linear regression with multiple variables. We obtained a good linear relationship, which reduced the influence of the matrix effect on the measurement results. According to the verification of the Certified Reference Materials for the Chemical Composition of Soils, except for individual elements, the method’s precision for determining nutrient elements is between 0.31%~4.21%, and the determination results are basically consistent with the certified values. This method is not only simple to operate and can avoid the environmental pollution caused by traditional methods, but it also can realize the simultaneous determination of multiple elements, which promotes the further development of LIBS technology in quantitative analysis.