The invention provides a method for extracting astaxanthin from haematococcus pluvialis, and belongs to the technical fields of bioprocess technology and chemical technology. The method comprises the following steps: completing the selection of raw materials through abnormal growth of cells of the selected haematococcus pluvialis, dilution of high-density algae cells and light induction, carrying out wall-breaking treatment on frond by using an ultrahigh pressure extractive technology, then extracting, eluting, concentrating, saponifying and centrifuging, thus obtaining the astaxanthin. The method has the advantages that the consumption of an organic solvent is little, an extraction agent can be circularly utilized, the environmental pollution is little, the production cost is low, the recovery rate is high, few impurities exist, the possibility of oxidative degradation of the astaxanthin is reduced, and the extraction quality of the astaxanthin is improved.