The invention provides a method for preparing antihypertensive peptide by using ridge bones of hairtail in a fermentation way. The method comprises the following steps: (1), sugar, crushed hairtail ridge bone, peptone, K2HPO4, MgSO4.7H2O and water are mixed to produce fermentation medium, after sterilization, bacillus licheniformis is inoculated, and is cultured to obtain fermentation liquid; (2), after the fermentation liquid is centrifuged, the supernatant liquid is taken and filtered, and enzyme sterilization is performed to the filter liquor; (3), the filter liquor after the enzyme sterilization is centrifuged, discoloring and smell removal are performed to the centrifuged supernatant liquid by activated carbon, so as to obtain the filter liquor after the discoloring and the smell removal; (4), the filter liquor after the discoloring and the smell removal is ultrafiltered to obtain permeation liquid, freeze drying is performed to the permeation liquid after vacuum concentration, and then peptide powder with antihypertensive function is obtained. The sources of the raw material adopted by the method of the invention are rich, the price is low, the operation is easy, and the method has stronger industrialized practicability.