Corrosion inhibitors can inhibit corrosion of metal in acidic medium effectively. However, most organic synthetic corrosion inhibitors are harmful to human and environment. Natural plant corrosion inhibitors applied in acidic medium were reviewed, and various extraction methods used in the preparation process were summarized, covering soaking method, Soxhlet extraction method and ultrasonic extraction method. Advantages and disadvantages of such research methods as weight-loss method and quantum chemical method, as well as technologies of improving plant corrosion inhibitor performance were illustrated. Function mechanism of plant corrosion inhibitors fell into the category of physicochemical function mechanism. In the practical research, research on plant corrosion inhibitors could be further promoted by selecting appropriate extraction method, taking function mechanism as theoretical guidance, and analyzing and characterizing plant extracts resorting to advanced research techniques. In addition, development of plant corrosion inhibitors was prospected, future development trends were expanding range of extraction and exploring industrial production and diversified application of plant corrosion inhibitors.