The invention discloses a portable vehicular heat insulation bag and relates to the field of heat insulation bag structures. The portable vehicular heat insulation bag comprises a bag body, wherein a sealing opening is formed in the bag body; a power base is arranged at an end opposite to the sealing opening; a connector connected to a vehicular power supply is arranged on the power base; the bag body is made of a flexible material and comprises a waterproof outer layer, a heat insulation layer, a heating layer and a waterproof inner layer sequentially from outside to inside; the heating layer is heat conducting silica gel, and multiple heating coils connected with the power base are uniformly distributed on the heating layer; an inward protruding structure is corresponding to the heating coil; a viscous material layer is arranged on one side of the inward protruding structure in an inner cavity of the bag body; a sensor is arranged between the viscous material layer and the protruding structure; and the sensor is connected with the power base and controls on/off of the heating coils in corresponding protruding structure. With a flexible heat insulation bag for heat insulation, the portable vehicular heat insulation bag disclosed by the invention has the advantages of convenience in carrying, no space occupation, convenience in application in a car and the like.