Discussion of xanthotoxin (8-MOP) inhibiting effect on human gastric carcinoma SGC - 7901 cells, its effection on autophagy and its mechanism in vitro. Determined by MTT assay to detect different concentrations (10,20,40,80,160 μg / mL) of 8-MOP effected SGC-7901 cells after 48 h. Autophagosome was observed by transmission electron microscope.The contents of calcium ions was assayed by confocal laser.8-MOP obviously inhibited the SGC-7901 cell proliferation, its inhibition was in relationship with concentration-response. Transmission electron microscope observation showed that it generated a lot of autophagosome. 8 - MOP made intracellular calcium ion concentration elevated and it was dose-dependent manner. Its mechanism might be associated with the increase of intracellular Ca2 + concentration.