The invention relates to a preparation method of Pleurotus eryngii soup, which comprises the following steps: rinsing raw material Pleurotus eryngii in a rinser, pulverizing in a pulverizer, granulating in a granulator, making Pleurotus eryngii pulp in a pulping machine, decocting in a soup decocting machine for 3-6 hours to obtain Pleurotus eryngii soup, canning, sterilizing, inspecting on an inspection platform to obtain qualified products, and boxing. The invention solves the problems of low income in spite of high yield of Pleurotus eryngii, unnecessary economic loss for people due to rotting of the Pleurotus eryngii which is hard to store, and severe waste of Pleurotus eryngii leftover resources, and enhances the utilization ratio of the Pleurotus eryngii Pleurotus eryngii and the added value of the Pleurotus eryngii; and the Pleurotus eryngii soup is convenient to carry and eat, fully utilizes the pure natural nutritive value of the Pleurotus eryngii, can be absorbed by the human body more easily, and enhances the immunological competence of the human body. The invention has the advantages of simple technical production line, high production efficiency, low investment and high income, is economical and practical, has an active action on environmental protection, has wide market prospects, and is suitable for popularization.