In order to construct the recycling system of fisheries tray, it is necessary to assess the cleaning effect. In this paper, a starch solution is used to make artificial fisheries tray that has homogeneous stain. According to the characteristic of starch and iodine, the cleaning effect can be measured with image processing by analyzing the relationship between the residue and total stain. Moreover, in order to confirm the evaluated accuracy of cleaning effect, a weighing method is used. And it is obvious that the result of the measurement with image processing is actually the same as those of weighing one. As a result, the evaluating method of stain elimination rate, with practicability, economics and high accuracy, is developed. The following results are obtained : 1) The accuracy of measurement with image processing is high. 2) The cleaning effect can be assessed in detail with image processing, and it is useful for controlling the cleaning condition. 3) Compared with a conventional method, the method with image processing is simpler and costs less time.