The invention provides a method for cultivating cucumber seedlings for biological tests of blight, which comprises the following steps of: immersing prepared cucumber seeds into a container in which sterile water is filled, putting the container on a constant-temperature shaker, and performing shake culture at the temperature of 25 DEG C and at the rotate speed of 90 revolutions/minute; stopping shaking until the cucumber seeds in the container germinate and sprouts grow to 0.5 centimeter; and sowing the germinated cucumber seeds in a seedling raising disc with a disinfected cultivation substrate, and putting the seedling raising disc into a 25 DEG C artificial climate chamber for culturing, wherein the photoperiod in the culturing process comprises 12 hours of illumination and 12 hours of darkness, the cucumber seeds are poured by nutrient solution, and the seedlings can be used for the biological tests of the blight after about 20 days. The method has the advantages that the seedling raising time can be shortened, the rate of germination is high, and due to the adoption of substrate cultivation, the cucumber seedlings are not influenced by factors such as soil microorganisms, soil structures and the like, so that the seedlings are uniform in growth.