The invention belongs to the technical field of tomato cultivation, and discloses a cultivating method for over-summer tomatoes in a greenhouse. The method comprises the steps of variety selection, cultivation of robust stocks and scions, grafting and management after the grafting, wherein the management after the grafting comprises the specific steps that grafted seedlings are placed in the plastic greenhouse under the airtight shading condition and watered with sufficient water, the air humidity is kept at 95% or above, the daytime temperature is 23-28 DEG C, and the temperature at night is15-22 DEG C; a plastic film is opened the next day, after three days, the air humidity is reduced to 76%-80%, the seedlings are exposed to light for 0.5-1 hour on the fourth day, for 1-2 hours on thefifth day and for 4-5 hours on the sixth day, from the seventh day, the seedlings are exposed to light all day, and after 7-8 days of wound healing, belts are loosened in time for transplanting the seedlings. According to the method, before sowing, disinfection treatment is conducted, harmful bacteria carried by seeds can be killed for preventing viruses, and the survival rate of the seeds is increased; grafting is conducted below cotyledons of the stocks, the grafting portions can be designed into trapezoid shapes, the contact area is large, and the survival rate is high.