The invention relates to a hyponitric chemical deburring liquid and a deburring method for an iron-based cylindrical coil spring. The deburring liquid is prepared by the following compositions according to per liter liquid 200 to 220 milliliters of hydrochloric acid, 20 to 30 milliliters of nitric acid, 15 to 20 micrograms of 2-hydroxybenzoic acid, 0.5 to 1.0 gram of gelatine, 1 to 2 grams of polyethyleneglycol, 2 to 3 grams of nonyl phenol polyethenoxy ether, the balance being water. The chemical deburring method comprises the following steps of: a). preparation of deburring liquid; b). deburring; c). cold-water washing; d). neutralizing treatment; e). cold-water washing; f). hot-water washing; g). drying; and h). immersion of rust-preventative oil. The deburring liquid has the advantages that: the content of the nitric acid in the deburring liquid is very low, thereby nitrogen oxide generated is very limited, consequently the deburring liquid has low pollution and is environment-friendly. Simultaneously, the deburring production process has simple operation, short working procedure time, and high burr removal rate, and is suitable for mass production of the cylindrical coil springs which have complex shapes and are difficult to perform mechanical deburring; and the surface finish quality of parts after deburring is high. Moreover, the raw materials of the deburring liquid are low in price and the energy consumption of the deburring treatment is low, thereby the method is favorable for saving the resources and reducing the production cost.