The invention discloses a method for inducing spontaneous cataract by a
medicine (a direction-regulating
inducer MNU). The method comprises the following inducing steps: a, firstly, selecting 280 mice for research; b, after the step a is completed, placing the mice in free equipment of special pathogens, where water and foods are free to the mice; c, after the step b is completed, randomly dividing the mice into a common control group, an MNU group, an MNU+
melatonin group and an MNU+ blank group; and d, after the step c is completed, performing visual movement behavior test on the mice, determining a reaction threshold value through a function of correct tracking reaction, setting initial stimulation as a sine mode of 0.200 weeks / degree and fixed 100% comparison, and then performing electroretinogram examination on the mice. According to the invention, the
melatonin is added into the
inducer MNU, so that free radicals can be directly removed, the generation of endogenous
antioxidant enzymes can be improved, the
melatonin treatment is beneficial to the generation of Cu-Zn-SOD and MnSOD, and the levels of lipid and
DNA peroxidation markers MDA and 8-OHdG are reduced.