The application discloses a battery pack, vehicle and control method for alleviating spreading of thermal runaway of a battery pack. The battery pack includes: a plurality of secondary batteries, a housing of each of which includes a weakened portion, so that a heat flow resulting from thermal runaway of the secondary battery is able to break through the weakened portion to be discharged; a spray pipeline which is arranged corresponding to and at a spacing from weakened portions of the secondary batteries, at least a portion of the spray pipeline corresponding to the weakened portions being a breakthrough region which is able to form an opening under an action of the heat flow, a spray medium in the spray pipeline being sprayed to an abnormal secondary battery in thermal runaway via the opening; where a weight A of the sprayed spray medium is determined according to an equation (0.8A)0.85×D/B≥2.6.