The invention discloses an LB solid culture medium preparing method. The method comprises the steps of S1, adding tryptone, yeast extract and sodium chloride to water to be dissolved, adjusting pH to be 7.1-7.3 with sodium hydroxide aqueous solution, adding agar powder, conducting uniform mixing, and conducting volume metering to obtain solution A; S2, conducting high-pressure sterilization on the solution A obtained from S1, reducing temperature to 45-55 DEG C, adding antibiotics, and conducting uniform shaking to obtain solution B; S3, adding the solution B obtained from S2 into a culture dish, regulating air speed to be 800-1200 r/min, conducting blowing for 60-80 min, and sealing the culture dish with a sterile sealing film to obtain the LB solid culture medium. By the adoption of the method, generation of condensate water during LB solid culture medium preparation is avoided, the situation that the culture medium is polluted by bacteria is avoided, waste is reduced, the storage time of the culture medium is prolonged, the bacterial solution absorption capacity of the culture medium is improved greatly, test time is shortened, and test efficiency is improved.