The invention discloses a starch potassium iodide micro-channel plastic film detection test strip and a preparation method and application thereof. A micro-channel of a micro-channel plastic film is partitioned into a plurality of different areas; the areas are filled with starch potassium iodide detection reagents of different concentrations; during detection, the test strips are directly inserted inside liquid under test; the final range of the concentration of an object under test is judged by observing the quantity of developing areas after a certain time. By adopting the starch potassium iodide micro-channel plastic film detection test strip, a detection result indicates the quantity of the developing areas instead of conventional color depth, and the capillary self-absorbing action is utilized, so that the advantages of high detection speed, easiness in operation, and vivid and clear result are realized. Compared with the conventional test paper, the starch potassium iodide micro-channel plastic film detection test strip has the advantages of resistance to extreme environments, long shelf life, high reagent utilization rate, high reliability, greater convenience and higher applicability. The starch potassium iodide micro-channel plastic film detection test strip can be widely applied to a plurality of fields of foods, water quality, industrial detection and the like.