The application of the invention relates to preparation methods of iopromide and an intermediate of the iopromide. The method specifically comprises the following steps: conducting a reduction reaction, an iodination reaction and an acylation reaction on a compound shown in the formula VI to prepare a compound shown in the formula III, and further preparing to obtain the iopromide. The method notonly avoids the generation of double acylation byproducts, but also effectively reduces the generation of byproducts in the preparation process, the intermediate is easy to separate and purify, and ahigh-purity product is obtained at a relatively high yield.