The invention relates to preparation of a medicine which is specially used for defecography, can be quickly changed from a liquid state to a gel state in the checking process and can be developed under X rays. The medicine is prepared by adding a material with a quick hardening property in the preparation process and water into a contrast agent taking metal salts (such as barium sulfate and the like) which are non-toxic and harmless, are not absorbed by human bodies and are high in atomic numbers as main materials. The formula has a reasonable design, the medicine is economic and practical and does not have any toxic or side effect, the detection result is accurate and reliable, and a favorable basis can be provided for clinical diagnosis and treatment.