The invention belongs to the technical field of chemical extraction of traditional Chinese medicine, particularly relates to an extraction method, a purification method and application of alkaloids inground beetles, and specifically provides an extraction method for extracting the alkaloids from the ground beetles, a purification method for the alkaloids obtained according to the extraction method, application of the alkaloids obtained according to the extraction method or the purified alkaloids obtained according to the purification method, and application of the alkaloids obtained accordingto the extraction method or the purified alkaloids obtained according to the purification method in growth inhibition of gastric carcinoma cells. The extraction method has the advantages that GBA18 can be obtained through separation; experimental determination proves that the obtained products have a good inhibiting effect on gastric cancer and bacteria, and the half lethal dose and the minimum lethal dose are within the safety usage range recommended by the Chinese pharmacopoeia; the technical defects that active ingredients in the ground beetles are unclear in the prior art and applicationof the ground beetles is seriously limited are overcome.