The invention discloses a composition for forming a prostate phantom, the prostate phantom and a preparation method and application of the prostate phantom. The composition comprises, by weight, 0.65-0.712% of agarose, 22-22.5 micromol/kg cesium chloride, 2.5-3.5% of carrageenan, 0.1-0.3% of sodium chloride, and 0.025-0.035% of sodium azide. The prostate phantom is formed by the composition. The prostate phantom formed by the composition has the same characteristics as real human prostate tissue. The preparation method of the prostate phantom has the advantages that technological conditions are easy to control, the repeatability is good, the percent of pass and production efficiency of the prostate phantom are improved, and the prostate phantom can be applied to radion localization, radiation dose evaluation and prostate examination models.