Abstract: Based on the classic preparation experiment of ammonium ferrous sulfate, we improved it from a simple task-type preparation experiment into a highly comprehensive and complete open experiment integrating principle exploration, efficient preparation, open design and interesting observation. In the experiment, the single crystal structures of FeSO₄∙7H₂O and (NH₄)₂Fe(SO₄)₂∙6H₂O are introduced, the stability of crystal state ferrous sulfate and ammonium ferrous sulfate in the air is studied, and interesting experiments such as making artificial "crystal snow", "transparent crème", and "emerald" are designed. In the experiment, the stereo microscope was introduced to observe the crystal morphology. This improved experiment optimizes the allocation of class hours, enriches the teaching content, broadens the experimental dimension, deepens the understanding of the principle and professional knowledge of the students via comparing, and achieves the purpose of improving the students' innovation consciousness, laboratory skill, analysis ability and comprehensive ability.