A method for extracting recombinant human serum albumin (rHSA) from transgenic rice grain is provided, comprising the steps of: 1) grinding dehusked rice containing rHSA into milled rice grain with a fineness of 80˜120 mesh, which is mixed with a extraction buffer in a w/v ratio of 1:5, then extracting at 55˜60° C. for 1˜3 hours to obtain mixture I; said extraction buffer comprises 10˜30 mM phosphate buffer, 10˜20 mM sodium acetate, 15˜30 mM ammonium sulfate and 5˜20 mM sodium caprylate and has a pH of 6.5˜8; 2) adjusting the pH of mixture I to 4.0˜4.5, followed by precipitating at room temperature for 3˜12 hours to obtain mixture II; 3) filtering the mixture II and collecting the filtrate, to obtain a solution containing high concentration of rHSA. The concentration of rHSA in the resultant solution is 650˜660 μg/mL, which increases by 1.15 times comparing to the extraction amount before improvement, and the amount of non-target protein is reduced by 2.46 times. The method provides a basis for subsequent purification of rHSA.