The invention belongs to microbial fermentation, and particularly relates to a preparation method of high-gel-strength, high-viscosity and high-acyl gellan gum. The preparation method comprises the process steps: sphingomonas sp. is inoculated to a fermentation medium with the high carbon-nitrogen ratio, wherein the fermentation medium is sterilized and contains a carbon source, a nitrogen sourceand necessary nutrient substances; the pH of the fermentation medium is adjusted for high-temperature aerated fermentation, fermentation is carried out for 20-30 hours, and sterile water and an oxygencarrying agent are supplemented; when the viscosity of a culture solution is not improved any longer or the fermentation period is less than or equal to 50 hours, fermentation is completed; and afterfermentation is completed, a fermentation solution is post-extracted, and the high-gel-strength, high-viscosity and high-acyl gellan gum is prepared. The technical problems that in the prior art, gellan gum has the low 0.5% aqueous solution viscosity, the low gel strength, the low acyl content and the like are solved, and the advantages that the prepared gellan gum product has the high acyl content, high dissolving speed, the high 0.5% aqueous solution viscosity, the high gel strength and the like are achieved.