The invention discloses a culture method for rapidly increasing beta-glucan content in coccolithophores, which comprises the following steps: inoculating coccolithophore seeds in a seawater culture solution of salinity 25-30 per mill, culturing in conditions of a temperature 15-25 DEG C and intensity of illumination 2,000-5,000Lux, and adding sodium dihydrogen phosphate of concentration 5g / L in the culture solution before coccolithophore mature bodies are collected, wherein the volume ratio of the seawater culture solution and sodium dihydrogen phosphate solution is 1,000:(0.8-1.2). In such a way, within the last 5-10 hours before collection, i.e. the period in which the cell density of coccolithophore mature bodies is the highest, the addition of sodium dihydrogen phosphate enables rapid metabolism of coccolithophore mature bodies and rapid increase of beta-glucan, resulting in a high cumulative yield, and because the coccolithophore mature bodies are collected after 5-10 hours, the consumption is less, the beta-glucan content in the coccolithophore mature bodies is high, up to over 22 pg / cell, the purity is up to over 93%, and the bioactivity is high.